BIOLOGY

Answers Worksheet - 1
Chapter - 1 (Life Processes)

Ans. 1. (a) Carbon dioxide is reduced and water is oxidized.

Ans. 2. (c) Starch
Ans. 3. (b) Transpiration and temperature regulation.
Ans. 4. (b) nucleus, chloroplast, vacuole, guard cell
Ans. 5. Trachea is surrounded by C-shaped cartilaginous rings which prevents the trachea from
collapsing when there is less air in it.

Ans. 6. The two upper chambers of human heart are called atria or auricles. The function of
these auricles is receiving blood from different parts of the body. The left auricle receives
oxygenated blood from the lungs through the pulmonary vein whereas the right part
receives deoxygenated blood from the other parts of the body through superior and inferior
vena cava.
Ans. 7. Saliva is the fluid present in our mouth cavity and the saliva secreted into the oral cavity
contains enzymes, salivary amylase and lysozyme. Salivary glands secrete amylase.
The chemical process of digestion is initiated in the oral cavity by the hydrolytic action
of the carbohydrate splitting enzyme, the salivary amylase. About 30 per cent of starch
is hydrolysed by this enzyme (optimum pH 6.8) into a disaccharide known as maltose.
Amylase is a digestive enzyme that acts on starch in food, breaking it down in to smaller
carbohydrate molecules. Without amylase, a person will be unable to digest starches and
sugars in the mouth. However, the pancreas also secretes amylase which will continue the
digestion and hence, digestion of starch will not stop completely.
Ans. 8. Breathing process consists of two phases : Inhalation and exhalation.
Inhalation is the process by which oxygen is taken in through nostrils. During inhalation
process, the ribs move upwards and outwards due to contraction of intercostal muscles.
The diaphragm is lowered so that the volume of thoracic cavity increases. As a result air is
moved inside the lungs through nostrils.
Ans. 9. The site of complete digestion of carbohydrates, proteins and fats in human beings is small
intestine of alimentary canal. On complete digestion, carbohydrates are converted into
glucose, proteins into amino acids and fats into fatty acids and glycerol.
Ans. 10. The following raw materials are required for photosynthesis :
(a) Carbon dioxide : Plants take carbon dioxide from air through the stomata present in
leaves. Aquatic plants get carbon dioxide found in water as a dissolved gas.
(b) Water : Plants take in water from the soil through roots.
(c) Chlorophyll : It is present in chloroplasts which are found in green portions of the
plants like leaves.
(d) Sunlight energy : It is trapped by chlorophyll present in chloroplasts of leaves.
Ans. 11.

Ans. 12. (a) (i) Right atrium of the heart receives deoxygenated blood from all parts of the body.
(ii) Pulmonary veins carry oxygenated blood from the lungs towards the heart.
(iii) Superior vena cava carries deoxygenated blood Superior
from upper part of the body to right atrium of Venacava

the heart.
(iv) Semilunar valve prevents back flow of blood Pulmonary
from aorta to left ventricle. veins

(b) Arteries carry blood away from heart and blood flows
Semilunar
with high pressure and with jerks so to withstand this Right valves
high pressure arteries have thick walls. Veins carry atrium
blood towards heart and blood flows continuously
with very little pressure. So, veins have thin walls as
compared to arteries.
Ans. 13. Amoeba follows holozoic nutrition. It involves the following steps :
(i) I ngestion : Amoeba engulfs the food by using its temporary finger like projections
called pseudopodia. This process is called ingestion. When a food particle comes into
contact with an Amoeba, it forms pseudopodia around it.
(ii) By phagocytosis process it engulfs its food.
(iii) Digestion : The food which is taken inside the amoeba forms a food vacuole. Many
enzymes are secreted into the food vacuole and the complex food molecule is converted
into simple and diffusible form.
(iv) Absorption and assimilation : The digested food is absorbed by the cell by diffusion
process.
(v) Egestion : The undigested residue which remains in vacuole is expelled out.
Pseudopodia Food engulfed Digested food Assimilation Undigested
forming within diffuses of food
Pseudopodia food vacuole food vacuole into cytoplasm digested food thrown out

Food
particle

(a) Ingestion (b) Forming food (c) Digestion (d) Absorption (e) Assimilation (f) Egestion
Vacuole
Different stages in the nutrition process of Amoeba

Ans. 14. (a) There are two kidneys in humans. Each kidney is bean shaped with outer dark cortex
and inner light medulla. Medulla is composed of finely striped structures called
pyramids.There are numerous microscopic units called nephrons which are present
internally in kidneys. Each kidney is about 12 cm long, 6 cm wide and 3 cm thick and
it weighs about 150 g. Nephrons are structural and functional unit of kidneys. A tube

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 called ureter arises from hilum of each kidney and
connects with urinary bladder. The front end of
ureter is expanded into kidney called the pelvis.
Renal artery supplies oxygenated blood to kidney
and renal vein carries away deoxygenated blood
from kidney.
(b) (i) Removal of urine / passing out of urine
(ii) Filtration of blood
(iii) Selective reabsorption of useful materials.
Ans. 15. (a) Two enzymes are maltase and invertase.
(b) Zymase converts glucose and fructose into
ethanol and carbon dioxide.
(c) Fermentation occurs in absence of oxygen that is in anaerobic conditions.
(d) C6H12O6 → 2C2H5OH + 2CO2
Glucose Ethanol
Ans. 16. (a) The peel should be taken from the lower surface of the leaf as numerous stomata
are present on lower surface of the leaf.
(b) Safranin is used to stain a leaf peel.
Ans. 17. Green plants are sources of energy for all organisms so, if they disappear then all herbivores
will die and eventually all carnivores. So, food chain will be disturbed and life would come
to an end.
Ans. 18. (d) Fermentation, a type of anaerobic respiration seen in organisms like yeast, involves
the partial oxidation of glucose and the release of ethanol and carbon dioxide as the
end products. The reason for the incomplete oxidation of glucose is the absence of
oxygen, not the products formed by the process. Thus, assertion is false, but reason is
true.
Ans. 19. (c) Pancreatic amylase is a starch splitting enzyme like salivary amylase, so it cannot
digest proteins. Thus assertion is true, but reason is false.
Ans. 20. (a) The pressure with which blood moves due to contraction of ventricles is termed as
the systolic pressure (upper value) and the pressure of the blood when ventricles
relax is known as diastolic pressure (lower value).
(b) The blood vessel that has the lowest blood pressure is vein.
(c) The sphygmomanometer is a device that is composed of an inflatable cuff, a
measuring unit, and a valve. It is a device that is used for measuring blood pressure.
(d) The blood exerts a certain amount of pressure on the blood vessels. This exerted
pressure on the wall of arteries is termed as blood pressure. The normal blood
pressure of a person is 120/80 mm Hg.
Ans. 21. (i) (d) heterotrophic nutrition
(ii) (a) Carbon dioxide is reduced and water is oxidized
(iii) (a) Plot 1 Open stomatal pore at 12 Noon
(iv) (a) six
(v) (c) Autotrophs Heterotrophs
Energy is obtained from organic sources obtain energy directly or
indirectly from other organisms

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 Answers Worksheet - 2
Chapter - 1 (Life Processes)

cytoplasm mitochondria
Ans. 1. (d) Glucose  → Pyruvate + Energy  → Carbon dioxide + Water
 + Energy
Ans. 2. (d) Trypsin - Proteins
Ans. 3. (d) Duodenum
Ans. 4. (b) Transpiration : creates a suction force which pulls water inside the plant.
Ans. 5. Liver secretes bile and it is stored in gall bladder.
OR
(1) Bile changes the acidic medium of food to alkaline medium so that the pancreatic
enzymes can act on it.
(2) It also emulsifies fats. / Breaks down the large fat globules into smaller particles.
Ans. 6. Selective reabsorption is the second step involved in urine formation in human beings and
it is named so as in this step certain selective substances like glucose, water and some
essential nutrients get reabsorbed through different parts of nephron.
Ans. 7. Yes, nutrition is a necessity for an organism due to the following reasons :
(a) Food provides us energy to carry out various metabolic activities and thus helps in the
survival of an organism.
(b) Food is required for growth, repair and reproduction of cells.
(c) It provides immunity against various pathogens.
(d) It helps in replacement of worn out cells.
(e) It provides energy to carry out various daily activities.
Ans. 8.
Aerobic respiration Anaerobic respiration
This process occurs in the presence of This process occurs in the absence of
oxygen. oxygen.
During this process glucose is completely During this process glucose is incompletely
oxidized to release carbon dioxide and oxidized. In yeast the products are ethanol
water. and carbon dioxide. In human beings the
products are lactic acid and carbon dioxide.
More amount of energy is released during Less amount of energy is released during
this process. this process.
It takes place in mitochondria. It takes place in cytoplasm.
Ans. 9. Yes, I agree with this statement. Respiration process occurs all the time in plants i.e.,
both in day and night. But photosynthesis occurs only during day time i.e., in presence
of sunlight. Carbon dioxide which is produced by plants during respiration is used by
photosynthesis process during day time and oxygen is released. But in night time as there
is no photosynthesis, so carbon dioxide evolved by respiration cannot be utilized by plants
and is released out.

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Ans. 10. (a) Fig. A represents open stomata and fig. B represents closed stomata.
(b) 1- stomata; 2- guard cells.
(c) Guard cells are kidney shaped cells which contain thick inner walls and thin outer
walls. During day time they perform photosynthesis due to the presence of chloroplasts
in them. Due to increase in solute concentration inside the guard cells, water from
subsidiary cells rushes inside by osmosis. As a result guard cells swell up. The thin
outer wall bulges out and thick inner wall is pulled inside thus stomata opens. During
night time reverse happens, water rushes out from the guard cells and they become
flaccid closing the stomatal pore. Thus, turgor pressure of guard cells helps in closing
and opening of stomata.
Ans. 11. (a) The components of transport system in highly organized plants are xylem and phloem.
The functions of these components are as follows :
(i) Xylem conducts water and mineral salts from roots upwards to different parts of
the plant.
(ii) Phloem translocates manufactured food from leaves to different parts of the plant.
(b) Importance of transpiration process in plants are :
(i) It provides cooling effect to plants.
(ii) It helps in ascent of sap from roots to upwards reaching to different parts of the
plant.
Ans. 12. Breathing involves inhalation and exhalation process where oxygen is taken in and carbon
dioxide is given out by the lungs or we can say there is exchange of gases between cells of
lungs and our environment.
Rate of breathing increases during vigorous exercise as the demand or need of oxygen by
our body increases. During vigorous exercise our body needs more energy, which demands
more intake of oxygen gas as this gas is used to oxidize glucose to release energy. Hence,
the exchange of gases needs to be faster thus, increasing the breathing rate.
Ans. 13. (i) In human beings, the blood passes twice through our heart so this type of circulation is
called double circulation. It consists of :
(a) Pulmonary circulation : Here deoxygenated blood from whole parts of body
through superior and inferior vena cava comes to right atrium. Then it passes to
right ventricle. Pulmonary artery carries this blood to lungs for oxygenation. Then
pulmonary veins carry oxygenated blood from lungs back to left atrium of heart
then the blood moves to the left ventricle. This is called pulmonary circulation.
(b) Systemic circulation : Here oxygenated blood from left atrium moves to left ventricle
and finally by aorta gets distributed to all parts of the body. This is called systemic
circulation.
Double circulation is necessary because it
keeps both oxygenated and deoxygenated
blood separated from each other. This makes
the circulatory system more efficient which
provides more energy required to maintain
constant body temperature.
(ii) Blood is called a liquid connective tissue as it
circulates through all the body parts carrying
nutrients, respiratory gases, hormones,
excretory substances etc. It supplies nutrients,
oxygen, hormones to various parts and removes Capillaries of body
excretory products, carbon dioxide from them. It apart from each other

consists of a liquid medium called plasma and it connects each parts of the body.

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Ans. 14. (a) Excretion is the process of removal of mainly nitrogenous wastes from the body.
(b) Nephron is the basic filtration unit present in kidney.
(c) Ultrafiltration, selective reabsorption and tubular secretion
are the three major steps involved in urine formation in
humans.
(d) (i) Nephrons present in kidneys form urine.
(ii) Ureter collects urine from kidneys.
(iii) Urinary bladder stores urine.
(iv) Renal artery supplies oxygenated blood to kidney.
Ans. 15. The steps for preparation of temporary mount of a leaf peel to
observe stomata include :
(a) A layer is peeled off from the lower surface of a leaf.
(b) It is stained with safranin and extra stain is rinsed off.
(c) A small portion from the peel is cut off and the peel is now placed on the slide.
(d) A drop of glycerine is placed on the slide and a cover slip is placed above it.
Ans. 16. (a) The artery is the blood vessel that has the highest blood pressure. The blood enters the
artery with immense pressure from ventricles. This is the reason that the arteries have
the highest blood pressure.
(b) The instrument that is helpful in measuring the blood pressure is a
sphygmomanometer. The sphygmomanometer can be used to measure both systolic
and diastolic pressure.
(c) The average systolic blood pressure is 120 mmHg and the average diastolic blood
pressure is 80 mmHg.
(d) The medical condition that is caused by an increase in blood pressure is hypertension.
Ans. 17. Plants have water and food transport system. Water transport system – roots absorb water
from the soil, Xylem is a tissue that conducts water from the roots to the upper part of plant.
Leaves prepare food for the plants → phloem is a tissues that conducts food from the leaves
to various parts of the plant.
Ans. 18. (c) Dark phase do not take place at night, it is independent of light, so light is
not a mandatory factor here. Thus assertion is true, but reason is false.
Ans. 19. (b) An Amoeba captures food using finger-like projections of its cytoplasm called
pseudopodia. The food particle is then ingested by surrounding it in cell membrane and
internalizing into the cell in a process called phagocytosis. In unicellular organisms, the
food is taken by the entire surface. Thus, both assertion and reason are true but reason
is not the correct explanation of the assertion.
Ans. 20. (a) The formation of urine takes place in the urinary system (Excretory system).
(b) Nephrons are the functional units of kidneys that produce urine.
(c) The waste fluid produced during metabolic activities is known as urine.
(d) Urethra is the final part of the urinary system. The function of this part is to remove
urine out of the body.
Ans. 21. (i) (d) Anemia
(ii) (a) Part/organ of human Function
respiratory system
Trachea cartilaginous tube that connects the mouth cavity
to the larynx
(iii) (d) (I), (II) and (IV) only
(iv) (a) Iron
(v) (b) In dissolved form

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 Answers Worksheet - 3
Chapter - 1 [Life Processes]

Ans. 1. (b) Yeast, mushroom, bread mould.

Ans. 2. (a) Heterotrophs do not synthesise their own food.
Ans. 3. (b) IV
Ans. 4. (b) Movement of water in and out of the guard cells.
Ans. 5. Alveolus is the respiratory unit and haemoglobin is the respiratory pigment of human
beings.
Ans. 6. Photolysis is the process of decomposition of water into hydrogen and hydroxyl ions.
This process uses photons of sunlight and takes place in grana during light phase of
photosynthesis reaction.
Ans. 7. Bile juice is secreted from liver. It helps in emulsification of fats i.e. it breaks large lipid
molecules into smaller globules so that lipase enzyme can easily convert these emulsified
fats into fatty acids and glycerol. It also makes the medium alkaline in small intestine so that
the enzymes of pancreatic juice and intestinal juice can activate and perform their respective
functions as the food that enters into small intestine from stomach is acidic in nature.
Ans. 8. Energy currency for cellular processes/ATP breaks down to give a fixed amount of energy
which can drive the endothermic reactions taking place in the cell.
Ans. 9. During summer season we lose most of the water through perspiration so we pass urine
fewer times. During summer we drink a lot of water and kidneys reabsorb more water
from the urine making the urine thicker as compared to winter season in order to maintain
the water balance in our body.
Ans. 10. (a) Pancreatic juice.
(b) Large intestine.
(c) Gastric juice containing pepsin enzyme, mucus, HCl.
(d) Diaphragm.
(e) Bicuspid valve.
(f) Glomerulus and Bowman’s capsule.
Ans. 11. (a) Two components of blood are : liquid part which is plasma and cellular component
which includes RBCs, WBCs, platelets.
(b) Oxygenated blood from lungs is carried by pulmonary veins ® left auricle ®left
ventricle ® Different body parts through aorta.

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(c)
Arteries Veins
Arteries have thick walls to withstand Veins have thin muscular walls as de-
high pressure of the oxygenated blood oxygenated blood flows with low pressure.
flow through them.
Arteries have no valves. Veins have valves to prevent back flow of the
blood.
Ans. 12.
Digestive glands Secretions Substrates
Salivary glands Saliva [ptyalin] Ptyalin act upon starch and
convert into maltose.
Gastric glands Gastric juice [pepsin enzyme, HCl, Pepsin enzyme present in
mucus] gastric juice acts upon proteins.
Pancreas Pancreatic juice [trypsin, lipase, Trypsin acts upon peptones and
amylase] proteins, amylase on starch and
lipase on fats.
Ans. 13. The three types of blood vessels are :
(a) Arteries (b) Veins (c) Capillaries
(a) Arteries : They carry oxygenated blood from the heart and transport it to different
organs.
(b) Veins : They carry deoxygenated blood from organs and take this blood to the heart.
(c) Capillaries : Capillaries are thinnest and smallest blood vessels. Exchange of material
between the blood and surrounding cells takes place across them.
Ans. 14. Mechanism of Urine Formation : The formation of urine occurs in three steps :
(a) Ultrafiltration : Blood flows under high pressure in glomerulus and the
liquid portion of the blood filter out from glomerulus and passes to the cup
shaped cavity of Bowman’s capsule and this process is called ultrafiltration.
(b) Selective reabsorption : It is the process of selective absorption of useful substances
like glucose, water, some salts etc., from glomerular filtrate which is obtained from
ultrafiltration by different parts of nephron.

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 (c) Tubular secretion : Some harmful substances like chemicals, drugs like penicillin,
potassium ions etc., are released by renal tubule to the forming urine called tubular
secretion.
(d) The formed urine is then received by collecting ducts which pours into the pelvis of
kidney.
Ans. 15. (a) Various respiratory organs and their specialised functions are as follows :
(i) Nostrils and nasal cavity : It is lined with mucus membrane and fine hairs which
trap dust, dirt, harmful bacteria and other foreign substances and prevent their
entry into the respiratory tract.
(ii) Trachea : It is the wind pipe through which air enters and it is divided into
bronchi and bronchioles so that each and every part of lungs can be supplied
with air.
(iii) Alveoli : These are thin walled, small sacs like structures present inside lungs,
spherical in shape which increase the respiratory surface thus providing efficient
gaseous exchange.
Thus we can say that each and every respiratory organ is structurally specialised
in its function.
(b) Nostrils ® nasal passage ® pharynx ® larynx ® trachea ® bronchi ® bronchioles ®
alveolar sacs.
Ans. 16. • The plant kept in dark is unable to carry out photosynthesis and due to absence of
oxygen it cannot respire.
• But the plant kept in light is able to photosynthesize converting CO2 into oxygen
which it can use for respiration.
Ans. 17. Precautions are :
(i) Germinating seeds should be moist.
(ii) Flask should be air tight.
(iii) Delivery tube must be immersed in water inside beaker.
(iv) KOH solution in a small vial must be kept inside conical flask.
Ans. 18. (a) In most animal tissues, oxidation is carried out by aerobic respiration. But
sometimes in aerobically respiring organisms, anaerobic metabolism take place in
certain tissues like skeletal muscles which do not get as much as oxygen required
and produce lactic acid. Thus both assertion and reason are true and reason is the
correct explanation of the assertion.

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Ans. 19. (a) During the day transpiration becomes the main driving force for pulling up of
water. But at night since there is no sunlight transpiration does not take place, so
water is pulled up due to root pressure. Thus, both assertion and reason are true
and reason is the correct explanation of the assertion.
Ans. 20. We know that pulse pressure is the difference between systolic and diastolic pressure. So,
let us take diastole pressure as X.
Systole pressure – Diastole pressure = Pulse pressure
140 – X = 40
X = 140 – 40 = 100 mm of Hg.
So, the diastolic pressure of the person is 100 mm of Hg.
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 Answers Worksheet - 4
Chapter - 2 [Control and Coordination]

Ans. 1. (d) Cytokinin.

Ans. 2. (c) Negative phototropism.
Ans. 3. (b) Under secretion of thyroxine.
Ans. 4. (b) Synapse.
Ans. 5. Neuron is the longest cell present in human body and medulla oblongata controls
involuntary actions like blood pressure, salivation, etc.
Ans. 6. Auxin hormone plays a role in apical dominance in plants and abscisic acid promotes
yellowing and senescence of leaves in plants.
Ans. 7.

When we step our feet on a sharp object we immediately remove our feet from the object.
Sharp object like pin is the stimuli and receptor organ is our feet. An impulse is created
which is carried by sensory neuron to spinal cord. Motor neuron carries the impulse
generated by spinal cord to effector i.e., muscles of our feet which withdraw our feet from
the sharp object.
This act is known as reflex action.
Ans. 8. Brain and spinal cord are covered by three layered membrane called meninges. The
outermost layer is called dura mater, middle thin delicate layer is arachnoid mater and
inner layer is pia mater. The space between the covering layers is filled with cerebrospinal
fluid which acts as a cushion to protect them from shocks and injuries.
Ans. 9. (a) Source gland is thyroid gland. Thyroxine regulates protein, carbohydrate and fat
metabolism in our body.
(b) Source gland is adrenal gland. It prepares the body to face the emergency situation by
increasing heart-beat, breathing rate etc.
Ans. 10. Synapse is a point of contact between the axon terminals of one neuron with the dendrite
of another neuron. The terminals of axon are swollen which contains a chemical called
acetylcholine, a neurotransmitter, which induce impulses in the dendrites of next neuron.
Synapse acts as one way valve which prevents the back flow of impulses from axon
terminals. So, impulse moves from dendrites through cyton to axon. It allows the nerve
impulses in one direction.

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Ans. 11. (a) The brain is divided into three main subparts : the forebrain, the midbrain, and the
hindbrain. The structure in front of the brain is the forebrain. The narrow region that
links the hindbrain with the forebrain is the midbrain. The structure present towards
the lower back of the skull is the hindbrain.
(b) The cerebellum is responsible for maintaining body posture.
(c) The medulla oblongata is the part of the brain that has the reflex centers for sneezing
and vomiting. Along with these function it also regulates involuntary actions
like breathing, heart rate, blood pressure, defecation, coughing, hiccupping and
swallowing.
(d) The brain is part of the central nervous system. The other part of the central nervous
system is the spinal cord.
Ans. 12. The function of nervous system is to control and coordinate all the voluntary and
involuntary actions in our body. Similarly hormonal system coordinate some functions of
our body by secreting chemicals called hormones by various endocrine glands. The
coordination between nervous and hormonal system is brought by hypothalamus which
secretes neurohormones. These neurohormones regulate the secretion of pituitary gland
which in turn regulates the activities of other endocrine glands. For example : In case of
emergency situation stimulus is perceived by receptors where impulse is carried to CNS
and message is conveyed. Effectors respond to the stimulus. Simultaneously, sympathetic
nervous system stimulates adrenal gland to release adrenaline which increases our heart
beat, breathing rate, etc. Thus from the above example we can say nervous and hormonal
systems together perform the functions of control and coordination in human beings.
Ans. 13. Neuron or nerve cell is the structural and functional
unit of nervous system. The three parts of the neuron
are cyton/cell body, dendrites, axon.
(i) Dendrites are fine, branched cytoplasmic
projections of cyton which are the site of receiving
information and they conduct these impulses to
cyton.
(ii) Cyton receives impulses from dendrites and
passes through axon. Cyton contain nucleus,
nissl’s granules and other cell organelles.
(iii) Axon is a long process from cyton which is
surrounded by an insulating sheath called myelin
sheath. Axon conducts nerve impulses away from
cyton. The terminals of axon are swollen which
contains chemicals called neurotransmitters. This
chemical sets a new impulse in the dendrites of
adjacent neurons.
Ans. 14. (a) A—Pituitary gland; B—Thyroid gland,
C—Adrenal gland; D—Pancreas; E—Ovaries;
F—Testes
(b) Pancreas secrete insulin and glucagon. These two hormones regulate blood glucose
level in our body.
(c) Ovaries secrete oestrogen, progesterone hormone whereas testes secrete testosterone.
(d) Thyroid gland secretes thyroxine hormone. Under-secretion of this hormone causes
goitre, cretinism in children, myxoedema in adults. Over-secretion causes
exophthalmic goitre.

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Ans. 15. Tropism is the directional movement of the part of the plant in response to external
stimulus. There are different types of tropism :
Phototropism : It is the directional movement of the plant part in response to light
stimulus. Example : Shoots of plants bends towards light, roots of plants bend away from
the light.
Geotropism : It is the orientation of the plant part in response to earth’s gravity.
Example : Roots of plants grow downwards in the soil in the direction of gravity.
Chemotropism : It is the directional movement or orientation of plant part in response
to chemical stimulus. Example : During fertilisation process, pollen tube grows towards
ovule in the ovary.
Hydrotropism : It is the directional movement or orientation of plant part in response to
water stimulus. Example : Bending of roots of the plant towards water.
Ans. 16.
Movement of leaves of a sensitive plant Movement of a shoot towards light
The type of movement of leaves of the sensitive The movement of shoot towards light is
plant is known as nastic movement. They take known as a tropic movement. It takes place
place immediately in response to the stimulus over a longer period of time.
of touch (thigmotropism).
This type of movement does not depend on the This movement depends on the direction of
direction of stimuli. light and is known as phototropism. This
type of movement is directional and growth
development.
Ans. 17. Receptors are specialised cells in our body which respond to the changes that occurs in
our body i.e., stimulus. They pass the information in the form of sensory impulses to
central nervous system through sensory nerves. If receptors will not work properly
impulses will not be generated in response to the stimuli and our body cannot provide
an appropriate response to the changing environment. For example, if olfactory receptors
will not work properly we cannot detect any smell whether it is good or bad.
Ans. 18. (a) Plant hormones help them to sense changes in the environment even if they don‘t
have eyes, ears or nose. Thus, both assertion and reason are true and reason is the
correct explanation of the assertion.
Ans. 19. (b) Synapse and neuron has no relation regarding function. Neuron is the functional unit
but that doesn‘t define synapse. Thus, both assertion and reason are true, but reason
is not the correct explanation of the assertion.
Ans. 20. (a) Diabetes
(b) Thyroxine
(c) Development of male sex organs
(d) Top of kidneys
Ans. 21. (i) (a) β cells of islets of Langerhans.
(ii) (a) Red Plot Green Plot Justification
Diabetic Normal Fasting blood glucose level are above 100 in diabetic
(iii) (a) Insulin
(iv) (a) Increased blood sugar
(v) (c) Hormone Gland Function
Testosterone Testes Development of eggs
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 Answers Worksheet - 5
Chapter - 2 [Control and Coordination]

Ans. 1. (d) All of these.

Ans. 2. (c) (ii), (iii)
Ans. 3. (c) Medulla in hind brain.
Ans. 4. (a) Pons - Consciousness.
Ans. 5. Testosterone hormone is responsible for the secondary sexual characters in male human
beings.
Ans. 6.  A nerve impulse begins when a neuron receives a chemical stimulus. A nerve impulse travels
along the neuron in the form of electrical and chemical signals. The axon tip ends at a synapse.
A synapse is the junction between each axon tip and the next structure. Movement of Na+
ions inside the axon membrane and that of K+ ions outside the membrane via ATP energised
pump generates action potential across the axon membrane which in turn generates the nerve
impulse.
(i) Dendrites are the small extension of nerve cells that receive signals from sensory receptors
or other neurons. Nerve impulses begin in a dendrite, move towards the cell body, and
then move down the axon.
(ii) An axon is a long, slender projection of a neuron that typically conducts electrical impulses
away from the neuron's cell body in the form of a wave of depolarization. The function of
the axon is to transmit information to different neurons, muscles and glands.
Ans. 7. (a) Growth dependent movements are called tropic movements.
(b) Non-growth dependent movements are nastic movements.
(c) The different phytohormones are :
1. Auxins, 2. Gibberellins, 3. Cytokinins, 4. Abscisic acid
(d) Auxins.
Ans. 8. Animals have endocrine glands which secrete hormones, the chemical messengers. These
hormones are poured directly into blood stream which is carried by blood to target
organs and they regulate various physiological processes. Suppose glucose level is more
in blood then the beta cells of pancreas gets triggered and synthesize large amount of
insulin which converts excess glucose into glycogen and stores in liver.
Ans. 9. Over production of growth hormones causes gigantism in children and acromegaly in
adults. Similarly under secretion of growth hormones causes dwarfism in children.
Ans. 10. (a) Auxins promote cell elongation and root formation.
Auxin is a growth stimulating hormone which promotes growth.
(b) Gibberellins stimulate seed germination and flowering.
Gibberellin is also a growth promoting hormone.
(c) Cytokinins promote cell division, breaks dormancy of seeds and buds.
(d) Abscisic acid causes dormancy of seeds.
It is a growth inhibitor which inhibits growth of plants.
Ans. 11. (a) The figure represents the phenomenon of phototropism i.e., response of plants to
light.

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 (b) The plant hormone auxin is involved in the phenomenon of phototropism.
(c) Plants show their growth towards light and this movement is caused by the action
of auxin hormone. Auxin is synthesized by the meristematic tissue which is present
at the tip of shoots, roots etc. In the above figure the plant bends towards the light.
Auxin hormone is synthesized in the tip of the stem and moves towards the side of
the plant which is not receiving light. Due to more auxin hormone in the region of the
plant that does not receive light, they grew faster than the part that receives light. So,
the stem bend towards the direction of light.
OR
When growing shoot is exposed to unidirectional light, it results in auxin shifting towards
the shaded side. More auxin causes more growth of shoot in the shaded side.
Ans. 12. (a)
Cerebrum Cerebellum
It is a part of forebrain and constitutes a It is a part of hind brain and lies below
major portion of brain. cerebrum.
It is seat of intelligence, memory, reasoning, It coordinates muscular activity and
will power. It controls voluntary actions. maintains balance, posture of our body.
(b) Nerves that arise from spinal cord are called spinal nerves and that arise from brain are
called cranial nerves. There are 12 pairs of cranial nerves and 31 pairs of spinal nerves in
the human body.
Ans. 13. (i) A: Sensory neuron or Nerve
B: Relay neuron or Interneuron
C: Effector
(ii) The functions of A and C are as follows:
A: The sensory neuron conducts the nerve impulses towards the Central Nervous
System (CNS). The CNS is comprised of the brain and the spinal cord.
C: The effector organ shows response by contracting or secreting a product.
(iii) Reflex arcs have been evolved in animals because the thinking process of the brain
is not fast enough. Many animals have very little or none of the complex neuron
network needed for thinking. So, it is quite likely that reflex arcs have evolved as
efficient way of functioning in the absence of true thought processes. However, even
after complex neuron networks have come into existence, reflex arcs continue to be
more efficient for quick responses.
Ans. 14. The immediate, involuntary and often unconscious responses against particular stimuli
are called as reflex actions.
Examples :
(i) Withdrawal of our hands on touching a hot plate.
(ii) Closing of our eyes when flashed with strong light.
Ans. 15.
Nervous Control Hormonal Control
Messages are sent as an electrical impulse. Messages are carried in the form of
chemicals (hormone)
It is carried through Neurons. It is carried through blood
Nerve impulses produce rapid responses. Hormones produce slow responses.
Nerve impulses produce short lived Hormones produce long lasting responses.
responses.

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Ans. 16. Brain and spinal cord are the two components of central nervous system in human beings.
Brain lies in the skull and spinal cord within the vertebral column. Peripheral nervous
system includes spinal nerves and cranial nerves which carry impulses to and from the
central nervous system. There are 12 pairs of cranial nerves and 31 pairs of spinal nerves.
Peripheral nervous system facilitates communication between central nervous system and
the other parts of the body. The two types of nerves are cranial nerves which arise from
brain and spreads throughout the head and spinal nerves which arises from spinal cord
and spreads throughout the body except head.
Brain and spinal cord are covered by a three layered membrane called meninges. The
outermost layer is called duramater, middle thin delicate layer is arachnoid mater and
inner layer is pia mater. The space between the covering layers is filled with a watery
fluid-cerebrospinal fluid which acts as a cushion to protect them from shocks and injury.
Ans. 17. Stimulus ¾® Receptor ¾® Sensory nerves ¾® Brain or spinal cord ¾® Motor neurons
¾® Effector ¾® Response.
Ans. 18. (a) Iodine is very necessary for the production of the hormone thyroxine, lack of
thyroxine causes goitre in the body. So, iodine is necessary to prevent goitre. Thus,
both assertion and reason are true and reason is the correct explanation of the
assertion.
Ans. 19. (a) Medulla controls circulation, respiration, reflexes like swallowing, coughing,
peristaltic movement of gut. So, damage to the medulla will stop circulation and
respiration and eventually cause death. Thus, both assertion and reason are true and
reason is the correct explanation of the assertion.
Ans. 20. (a) The plant hormone that regulates phototropism is auxin.
(b) The plant hormone that stimulates the shedding of leaves and fruits is ethylene.
(c) The plant hormone that helps stimulates the opening and closing of stomata is
abscisic acid.
(d) The plant hormone that participates in the process of thigmotropism is ethylene.
Ans. 21. (i) (a) Auxin.
(ii) (d) W  hen light is coming from one side of the plant, auxin diffuses towards the sunny
side of the shoot.
(iii) (b) Auxin.
(iv) (d) Both (a) and (b).
(v) (c) Hormone Function
Ethylene prevents ripening of fruits.
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 Answers Worksheet - 6
Chapter - 2 [Control and Coordination]

Ans. 1. (d) (i), (ii), (iii)

Ans. 2. (c) Rapid cell division in tendrillar cells that are away from the support
Ans. Part of the Brain Name
(c) Hind brain Cerebellum
Ans. 4. (c) Abscisic acid.
Ans. 5. Diabetes.
Ans. 6. Hypothalamus.
Ans. 7. The movement of tendril around a support is caused by the action of auxin hormone.
Auxin which is synthesized at the tip diffuses from the tip to the region that is away from
the support. The region containing more auxin will grow faster than the part which is in
contact with the support causing the tendril to curl around the support.
Example : Movement shown by tendrils of climbing plants like cucumber around solid
objects.
Stem tendril

Bomboo stick Leaf

for support Weak tendril
Bomboo stick
stem
of support

Ans. 8. Insulin is secreted by beta cells of Islets of Langerhans of pancreas. They convert excess
glucose to glycogen stored in liver thus lowering glucose level in the blood. In diabetes
patients, the sufficient amount of insulin is not secreted by pancreas so they have high
sugar level in their blood. To control the sugar level they are treated by giving insulin
injections.
Ans. 9. X is abscisic acid. Abscisic acid is a plant hormone which causes stomatal closure. Auxin
and gibberellins are two hormones which can reverse the effect of abscisic acid on plant
growth.
Abscisic acid is growth inhibitor which retards plant growth, promotes closing of
stomata. But auxins and gibberellins are growth promoters which stimulate plant growth.
They promote cell enlargement and cell differentiation, promote stem and fruit growth.
Similarly cytokinin promotes opening of stomata.
Ans. 10. Adrenaline hormone in the adrenal gland is secreted in scary situations in human beings.
Adrenaline hormone is also called as an emergency hormone. It is produced in the
medulla in the adrenal glands as well as some of the central nervous system's neurons.
Within a couple of minutes during a stressful situation, it is quickly released into the
blood, sending impulses to organs to create a specific response. After the stress has
subsided, adrenaline’s effect can last for up to an hour.

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 The impact of adrenaline release in our body are as follows:
1. Adrenaline triggers the body's fight-or-flight response. This reaction causes air
passages to dilate to provide the muscles with the oxygen they need to either fight
danger or flee.
2. It also triggers the blood vessels to contract to re-direct blood towards major muscle
groups, including the heart and lungs.
3. The body's ability to feel pain also decreases as a result of adrenaline.
4. Blood vessels dilate (enlarge) in our muscles.
5. Blood vessels constrict in our digestive tract to slow digestion.
6. Kidneys make more renin (to increase blood pressure).
7. Glucose production increases, for energy..
Ans. 11. Iodine is an essential component for synthesis of thyroxine hormone. Thyroxine hormone
is secreted by thyroid gland which regulates the basal metabolism of our body by
oxidation of carbohydrates, proteins and fats. It regulates the general growth of our body
and deficiency of this hormone leads to disorders like simple goitre, cretinism, myxedema
etc. So, it is advised to use iodised salt in our food.
Ans. 12. The orientation of plant part in response to water is called hydrotropism.
Activity to demonstrate hydrotropism : Two glass troughs A and B were taken. Both the
troughs were filled with soil upto two-third level. A tiny seedling was placed in both the
troughs. A small clay pot with soil was placed in trough B. In trough A water was added
uniformly to the soil but in trough B water was put only in small clay pot.
Observations : After few days it was noticed that in trough A roots of the seedlings had
grown straight as water is added uniformly to the soil. But in trough B roots of seedling
had grown in the direction towards the clay pot because water is contained in the clay
pot. This shows that roots of plant shows its growth in the direction of water.

Ans. 13. (a) Multicellular organisms are highly complex. Every activity need to be regulated so
that the activities can occur in proper time and correct sequence. Various organs
and parts of the body should work together in a coordinate manner to perform a
particular function. For proper control and coordination in higher organisms both
nervous and endocrine system plays a major role. For example : While riding a
bicycle there should be proper coordination between our hands and handle of our
cycle.
(b) The actions that are performed according to our will and are controlled by our
conscious thoughts are called voluntary actions. The actions that are performed
unconsciously and are not controlled by our will are called involuntary actions.
(i) Involuntary action (ii) Involuntary action
(iii) Voluntary action (iv) Involuntary action
Ans. 14. (a) (i) A is dendrite; B is axon.
(ii) End of dendrite acquires information in the neuron.
(iii) Information travels from dendrites to cyton and then along the axon towards
axon terminals.

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 (iv) Information travels in the form of impulse.
(v) At the end of axon terminals/nerve endings impulse is converted into chemical
signal for transmission.
(b) Thyroid gland secretes thyroxine hormone which regulates carbohydrate, fat, protein
metabolism in our body.
Ans. 15.
Organs Sympathetic nervous system Parasympathetic nervous system
Lungs Dilates bronchi and bronchioles. Constricts bronchi and bronchiole.

Heart Increases heart rate. Decreases heart rate.

Salivary gland Inhibits saliva secretion which Stimulates saliva secretion.
causes dryness of the mouth.
Pupil of eye Dilation Constriction
Ans. 16. Chemotropism is shown by pollen grains. The orientation or movement of plant parts in
response to chemicals is called chemotropism. Ovary produces some sugary substances
which are chemicals and in response to these chemicals pollen grains germinate and
develop pollen tube that moves through style to reach ovule present in ovary.
Ans. 17. (a) Touch is the stimulus which is common for movement in both the cases.
(b) Drooping of leaves in touch-me-not plant is an example of growth independent
movement which occurs due to change in turgur pressure of the cells. But attaching of
pea plant to a support with the help of tendrils is a growth dependent movement. The
pea plants develop tendrils which are sensitive to touch. When they come in contact
with a support they encircle the support and clings to them. Auxin hormone plays an
important role. Auxin synthesized at the tip diffuses to parts away from the support,
so those parts away from support grow faster than those parts in contact. So, the
tendrils encircle the support.
(c) Drooping of leaves in touch-me-not plant is an example of seismonastic movement
whereas attaching of pea plant to a support with the help of tendrils is an example of
curvature movement.
Ans. 18. (c) Thigmonasty is the movement of plant part in response to the touch of an object.
Thus, assertion is true, but reason is false.
Ans. 19. (c) Cerebellum which controls body posture and cerebrum is not connected to internal
ear. Thus, assertion is true, but reason is false.
Ans. 20. Digestion of food will be hampered as exocrine part of pancreas produces digestive juices
that help in digestion in small intestine.

••

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 Progress Check - 1

Ans. 1. (d) Nostrils ® Pharynx ® Larynx ® Trachea® Alveoli

Ans. 2. (c) Axonal terminals.

Ans. 3. (c)

Ans. 4. (a) spinal cord

Ans. 5. Salivary amylase present in saliva secreted by salivary glands present in our mouth is the
first enzyme to mix with food in the digestive tract.
Ans. 6. (a) Tracheids and vessel elements are the two kinds of cells in xylem. Tracheids are long,
narrow cells that overlap at their tapered ends. Vessel elements are short, wide-barrel
shaped conducting cells.
(b) Phloem tissue contains two cells: sieve tube elements, and companion cells. These
two components of phloem help in the transportation of food. Sieve tube elements are
elongated living cells but they lack a nucleus and have little cytoplasm. The
companion cells are located very close with the sieve tube elements.
(c) The release of water in the form of water vapour from the aerial parts of the plant is
called transpiration.
(d) Mosses are non vascular plants as they do have vascular conducting tissues.
They have internal conducting tissues, but xylem and phloem are absent. Thus,
mosses are plants that lack xylem and phloem.
Ans. 7.

Ans. 8. Figure (a) is more accurate as roots are positively geotropic so they move towards the
ground [earth’s gravity] and shoots are negatively geotropic and positively phototropic so
they move away from the ground [earth’s surface].
Ans. 9. (a) Lack of iodine in diet as iodine is an important element required for the synthesis of
thyroxine hormone from thyroid gland. Deficiency of thyroxine causes simple goitre
which can be observed as a swollen neck in people.

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 (b) Over secretion of growth hormone from pituitary gland in childhood causes
gigantism where the hands and legs of the person grow abnormally large.
(c) There is proper secretion of testosterone hormone which is responsible for
development of facial hairs, a secondary sexual character in males which is observed
during puberty.
Ans. 10. The major events during photosynthesis are :
(a) Absorption of light energy by chlorophyll : The chlorophyll pigment present within
chloroplasts traps sunlight energy in the form of photons which is required to split
water molecules. This is the first and important step of photosynthesis.
(b) Conversion of light energy into chemical energy and photolysis of water : Photons
split water molecules into hydrogen and oxygen. This is called photolysis of water
i.e., splitting of water molecules in the presence of sunlight energy. Oxygen is
released as by-product, an important gas evolved during photosynthesis.
The above two steps occurs in presence of light so they are called light phase
reactions.
(c) Reduction of carbon dioxide to carbohydrates : This process does not require
sunlight, so this phase is also called dark phase. Carbon dioxide with the help of
certain enzymes gets converted into glucose—the major food of all living organisms.
Ans. 11. (a) Auxin or Gibberellin (b) Cytokinin
(c) Abscisic acid (d) Abscisic acid
Ans. 12. Oxygen from air enters through nostrils, nasal passage, pharynx, larynx, trachea, bronchi,
bronchioles and finally to alveoli during inhalation. Alveoli are surrounded with blood
vessels where gaseous exchange occurs i.e., oxygen diffuses inside the blood vessels and
carbon dioxide diffuses out from the blood vessels into alveoli. Oxygen then combines
with haemoglobin present in blood to form oxy-haemoglobin and is carried to heart by
pulmonary veins and then it is transported to the rest parts of the body.
Carbon dioxide is transported mainly in dissolved form in the blood stream given out by
tissues during cellular respiration and is carried to the alveoli present in lungs where it
diffuses out to the alveoli from blood stream and is exhaled out through the nostrils.
Ans. 13. (i) Human heart is four chambered. It consists of two upper chambers called auricles or
atrium and two lower chambers called ventricles.
(ii) The right atrium receives
deoxygenated blood from all parts
of the body through two vena
cava—superior and inferior. The
opening between right atrium
and right ventricle is guarded by
tricuspid valve which prevents back
flow of the blood.
(iii) Pulmonary artery carries
deoxygenated blood from right
ventricle to lungs for oxygenation.
(iv) Left atrium receives oxygenated
blood from lungs through
pulmonary veins. The opening
of left atrium and left ventricle is
guarded by bicuspid valve.
(v) From left ventricle arises aorta which carries oxygenated blood to whole parts of
the body.
(vi) Human heart is enclosed by pericardium membrane.

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Ans. 14. The other name of tissue fluid is interstitial fluid. Its two functions are :
1. To provide a medium for the exchange of nutrients and waste products between cells and
blood.
2. To maintain the hydration and pressure of cells.
Ans. 15. The steps to be followed are :
(a) Clean the microscope and the lenses.
(b) Place the slide on the stage.
(c) Place the low power objective lens above the slide.
(d) Focus the material with the help of a coarse adjustment.
(e) Sharpen the focus with fine adjustment.
(f) Bring high power objective lens over the slide.
Ans. 16. The timing and amount of hormone released are regulated by feedback mechanisms.
Example – • If the sugar level in the blood rises more insulin is produced.
• As blood sugar level falls, insulin secretion is reduced..
Ans. 17. A person diagnosed with kidney failure can undergo kidney transplantation other than
dialysis. It is the transplant of a kidney into a patient with end-stage renal disease. A
healthy donor can donate his or her kidney to the patient via surgery.
Ans. 18. (a)  Pulse rate is the number of heart beats per minute. So, by counting the pulse rate we
can understand the heart beat and in turn understand the working condition of the
heart. Thus, both assertion and reason are true and reason is the correct explanation
of the assertion.
Ans. 19. (a)  Insulin is a hormone released by the beta cells of the pancreas. It maintains the
blood glucose level in the body, by its proper utilization. So, lack of insulin causes
accumulation of glucose in the blood and hence a disease called diabetes mellitus is
caused. Thus, both assertion and reason are true and reason is the correct explanation
of the assertion.
Ans. 20. (a) The forebrain of the brain contains an area known as the cerebrum. This area is
composed of the cerebral cortex.
(b) The cerebellum is located in the hindbrain. The structure present toward the lower
back of the skull is the hindbrain.
(c) The major part of the brain that is involved in thinking is the forebrain.
(d) The nerves that arise from the spinal cord are called spinal nerves.
Ans. 21. (i) (a) Proteolytic enzyme
(ii) (b) Pepsinogen to pepsin
(iii) (a) No digestion of egg white
(iv) (b) E  nzyme A is active only in the acidic environment, and it breaks down the large
polypeptides into smaller peptide fragments.
(v) (b) B- 4- (i), C-2- (iv), D- 1- (ii), A- 3- (iii)
Ans. 22. (i) (b) Gibberellin
(ii) (d) Cytokines
(iii) (d) Phytohormone
(iv) (b) inducing dormancy
(v) (c) Auxin

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 Answers Worksheet - 7
Chapter - 3 [How do Organisms
Reproduce?]
Ans. 1. (a) general growth rate begin to show down.
Ans. 2. (b) Yeast.
Ans. 3. (d) Pollen grains.
Ans. 4. (b) Genetic material comes from two parents of the same species
Ans. 5. Hibiscus is an example of a flower which contains both stamens and carpels.
Ans. 6. The process is called budding.

Ans. 7. (a) Ovary

(b) Anther
(c) Style
(d) Stigma
Ans. 8. (i) The nucleus in a matured Amoeba elongates and divides
into two.
(ii) A constriction appears in the middle of cytoplasm.
(iii) The constriction deepens and finally it divides.
(iv) Thus, two daughter Amoeba are formed from a single parent Amoeba.

Ans. 9. (a) The fertilized egg (zygote) starts dividing to form embryo and gets implanted in the
lining of uterus.
(b) The inner lining of uterus slowly breaks and comes out through the vagina as blood
and mucous.
Ans. 10. (a) AIDS is a sexually transmitted disease. Its causative agent is HIV.
(b) Awareness and safety measures for a healthy life.

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Ans. 11. This process is called regeneration and example is Hydra.
When Planaria is cut into three pieces each piece grow into separate individual.

Planaria

Planaria
Planaria
Ans. 12. (a) Ovary produces eggs and female sex hormones.
(b) Fallopian tube is the site of fertilization and it allows egg to move from ovary to the
uterus.
(c) Uterus receives the zygote and implantation of zygote occurs, it provides
nourishment to the growing embryo.
Ans. 13. (a) The process is known as spore formation in Rhizopus.
(b) Spore is covered by a thick structure to withstand unfavorable conditions like
drought, high temperature etc., so that they can survive for a long time.
(c) Hyphae are long, thread, branched filaments of fungus which release enzymes to
absorb nutrients from food sources.
Ans. 14. Pollination Fertilization
The process of transfer The process of fusion of
of pollen grains from male and female gametes
anthers of stamens to the to produce the zygote is
stigma of carpel within called fertilization.
the same flower or
different flower of same
plant or to any other
flower of different plant
but of same species is
called pollination.
Pollination is of two Fertilization is of two
types : cross and self types—external and
pollination. internal.

The site of fertilization in flower is inside ovary of female part of a flower. After
fertilization ovary becomes fruit and ovules become seeds.
Ans. 15. The growth of new plants from vegetative parts of the plant like roots, stem, leaves
other than the seeds is called vegetative propagation. Various methods of vegetative
propagation are :
(a) Cutting : Small piece of plant part like roots, stem or leaves is cut and is used for
propagation. Examples : Rose, china-rose, sugarcane, etc.
(b) Layering : It is the process where roots are induced when a stem comes in contact
with the ground. Examples : Grapevine, jasmine, litchi, mango, etc.
(c) Grafting : It is a process of joining a part of a living plant like stem or bud to another
plant and they grow as one plant. Examples : Lime, lemon, etc.
(d) Propagation by plant tissue culture : In this method plant cells are cultured in an
artificial culture media, where a cell divides into undifferentiated mass of cells called
callus which is transferred to different nutrient medium to grow into plantlets.

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 All the above methods are artificial methods of vegetative propagation.
In natural methods of vegetative propagation underground roots [root tubers of Dahlia] or
underground stems [bulbs of onions, rhizomes of ginger] or adventitious buds on leaves
[Bryophyllum] grow into new plants.
Ans. 16. (a) (i) Seminiferous tubules ® Epididymis ® Sperm duct ® Urethra.
(ii) Seminal vesicles secretion serves as a medium for transportation of sperms and
also they activate and nourish the sperms. The secretion of prostate gland makes
the medium alkaline and neutralizes the acidic medium of female vagina.
(b) For an organism to survive it has to perform various life processes like nutrition,
respiration, circulation, excretion etc. Reproduction is not required for survival of an
organism. During reproduction there is replication of DNA and only genetic material
is transferred from one generation to the next generation producing certain
variations. This process helps in maintaining the continuity of a species.
Ans. 17. (a) The part of the brain that controls and regulates the release of hormones is the
hypothalamus. This is because it releases certain molecules called hormone-releasing
factors that stimulate the production of hormones.
(b) The two endocrine glands which are common in both males and females are the
pituitary gland and the thyroid gland.
(c) The endocrine gland, which is present only in the males is testis. It produces a
hormone named testosterone.
(d) The endocrine gland, which is present only in the females is ovary. It produces the
hormones progesterone and estrogen.
Ans. 18. (c) Unisexual flowers are those which can have either stamen or carpels as sex organ. It
is not true that it has only stamen in it. It can have only carpel also, so either of these
will describe a unisexual flower. Thus, assertion is true but reason is false.
Ans. 19. (a) Both the sperm and ovum have 23 chromosomes, so when the zygote is formed
after their fusion there are 46 chromosomes in the zygote, and hence the number of
chromosome is restored in the offspring. Thus, both assertion and reason are true and
reason is the correct explanation of the assertion.
Ans. 20. (a) There are a number of diseases that are caused by sexual intercourse. These diseases
are called STDs “Sexually transmitted disease”.
(b) Treponema pallidum is the bacterium that causes a disease called syphilis in humans.
(c) The contraceptive device that is commonly used by the males is the condom.
(d) The vas deferens is cut in the process of vasectomy. This prevents the sperms from
reaching the ejaculatory duct.
Ans. 21. (i) (d) 1-5 days.
(ii) (c) Oviduct.
(iii) (b) degenerates in a short time.
(iv) (d) Epididymis → vas deferens → urethra.
(v) (c) Foetus human baby.
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 Answers Worksheet - 8
Chapter - 3 [How do Organisms
Reproduce?]
Ans. 1. (d) Menstruation.
Ans. 2. (d) Cracking of voice.
Ans. 3. (c) ‘X’ and ‘Y’ only
Ans. 4. (b) Hepatitis.
Ans. 5. 1. Testes are the primary sex organs in human males which produce sperms by the
process of spermatogenesis.
2. Testes also produce male sex hormone testosterone which helps in the development of
secondary male characteristics at the time of puberty.
Ans. 6. (a) X is Ovule, Y is embryo sac which contain egg cell and two polar nuclei.
(b) Grafting method is used.
Ans. 7. The Pre-natal Diagnostic Techniques (Regulation and Prevention of Misuse) Act, 1994,
was enacted and brought into operation from 1st January, 1996, in order to check female
foeticide. The Act prohibits determination and disclosure of the sex of foetus. It also
prohibits any advertisements relating to pre-natal determination of sex and prescribes
punishment for its contravention. The person who contravenes the provisions of this Act
is punishable with imprisonment and fine.
Ans. 8.
Binary fission Multiple fission
A single parent cell divides into two daughter A single parent cell divides and results in
cells. production of many daughter cells.
Nucleus divides once and then each nucleus Nucleus divides repeatedly to form many
gets surrounded by cytoplasm to form two nuclei and each gets surrounded by
individuals. cytoplasm to form many daughter cells.
It occurs under favorable conditions. Example: It occurs under unfavorable conditions.
Binary fission in Amoeba, Paramecium. Example : Plasmodium.
Ans. 9. The embryo gets nourishment inside the mother’s body through a disc shaped structure
called placenta. It connects embryo with mother’s blood. It supplies nutrients, oxygen
to the growing embryo and removes carbon dioxide, wastes from embryo. Through
this structure the blood of embryo comes in close contact with mother’s blood and by
diffusion process exchange of nutrients occurs. The placenta is formed by interlocking of
two sets of villi, which provides maximum surface area for absorption of nutrients and
oxygen gas.
Ans. 10. In sexual reproduction male and female gametes from two different individuals unite
leading to variations in offsprings due to mixing up of genetic material whereas in case of
asexual reproduction only single parent is involved and there is no formation of gametes.
The offsprings that are produced sexually have better chances of survival as due to
mixing up of genetic material between two different individuals there is increase in
genetic variations in the offsprings which provides maximum chances for the survival
of species in the changing environment as well as under unfavorable conditions. This
variation in species is also essential for evolution.

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Ans. 11. (a) Figure A is Hydra, B is Rhizopus, C is leaf of Bryophyllum and D is Planaria.
(b) Reproduction process is shown in all these figures. This type of reproduction is called
asexual reproduction where one single parent is involved without any formation of
gametes.
(c) Reproduction is the life process of an organism which helps in its growth of
population by forming new individuals. It helps to replenish the lost individuals.
OR
(i) (a) Buds present on the leaf margins in notches begin to grow to give rise to a new
plant – Vegetative propagation.
(b) Each part of Planaria grows into complete organism –Regeneration.
(c) The spores begin to grow after reaching a suitable moist surface – Spore formation.
(ii) • Zygote divides several times to form an embryo within the ovule.
• Ovule develops a tough coat and is converted into seed.
• Ovary grows rapidly and ripens to form a fruit.
• Petals, sepals, stamens, style and stigma may shrivel and fall off.
Ans. 12. (a) The figure represents female reproductive system.
(b) The figure is as shown.
(c) Ovary is the female primary sex organs which
produce ova or eggs.
Oviduct receives the egg released from ovum
and it is the site of fertilization.

Uterus is a muscular organ where
implantation of zygote occurs and it takes care
of the developing embryo.
Vagina is a muscular tube like structure which receives the sperms and through
which the baby is delivered.
Ans. 13. The methods or devices used to prevent fertilization and implantation are referred to as
contraceptive methods. Some of the methods are :
(a) Barrier methods : Use of condoms in male and diaphragms in female prevents the
entry of sperms into uterus.
(b) Chemical methods : Use of various hormonal pills prevents the release of egg from
ovary. They cause a change in menstrual cycle thus delaying ovulation.
(c) IUCDs : Use of IUCDs devices like copper-T which is fitted inside uterus that
prevents implantation of embryo into the wall of uterus.
(d) Surgical methods : Tubectomy is done in female where a small portion of oviducts
are removed and ligated to prevent the entry of egg from ovaries. Vasectomy is done
in males where a small portion of vas deferens is cut and ligated preventing passage
of sperms.
Chemical method is not meant for males.
Use of these techniques have direct impact on health and prosperity of family by :
(a) Preventing unwanted pregnancies to control population growth.
(b) Protecting from sexually transmitted diseases like AIDS, Syphilis etc.
(c) Proper health care of mother and child by preventing frequent pregnancies.
(d) Providing sufficient gap between the offsprings for proper care of the children.

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Ans. 14. (a) Testes are the primary sex organs in a human male which produce sperms by the
process of spermatogenesis. They also produce male sex hormone testosterone which
helps in the development of secondary male characteristics at the time of puberty.
(b) Vas deferens also called sperm ducts that carries the sperms from testes to urethra.
(c) Epididymis stores the sperms for some days where they get mature and become motile
in nature.
(d) Scrotum or scrotal sacs are pouch like structures located outside the abdomen in which
testes are placed. It provides an optimum temperature for sperm formation.
(e) The secretion of seminal vesicles helps in transportation of sperms and provides
nourishment to the sperms.
Ans. 15. Cotyledons store food for the growth of embryo.
Radicle becomes root in future plant.
Plumule becomes shoot in future plant.
Ans. 16. (a) Sperm formation will be adversely affected because it
requires a lower temperature than the body temperature.
(b) Vas deferens is a passage for transfer of sperms, so sperms will not be transferred
further.
(c) When prostate and seminal vesicles are not functional, they will not add secretions for
nourishment and medium for the transport of sperms.
(d) When an egg is not fertilized in a human female, it lives for about one day. Then, the
thickened lining of the uterus breaks leading to discharge of blood and mucus along
with the unfertilized egg. This is called menstruation.
(e) Nutrition and oxygen will not be provided to the growing embryo affecting its growth,
which could have serious implications as well.
Ans. 17. (a) There are two types of pollination self-pollination and cross-pollination.
The difference between self-pollination and cross-pollination are given below:
Self-pollination Cross-pollination
The process of transfer of pollen grains The process of transfer of pollen grains
from anthers to the stigma of a flower, but between the flowers of the different plants of
when this process is between the flowers the same species is called cross-pollination.
of the same plant than the process is called
self-pollination.
It involves single plant Involves two different plants of the same
species.
It occurs in perfect flowers only. It occurs in both imperfect and perfect flowers.
Pollinating agents are not required. Pollinating agent such as wind, water, insects,
etc. are required.
(b) Fertilisation is the process of fusion of the female gamete (ovum or egg) and the male
gamete produced in the pollen tube by the pollen grains. Post- fertilization the ovary
develops into the fruit while the ovary wall develops into pericarp.
Ans. 18. (c) The assertion is correct but reason is incorrect because ovulation takes place on the
14th day of the menstrual cycle, so if the sperm happens to meet the ovum during that
phase fertilization will take place. Sperm activity does not depend upon the phase of
menstrual cycle. Thus assertion is true, but reason is false.

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Ans. 19. (b) Both the statement are true but the reason that males have 2 testes and because of it
they descend into the scrotum this is not the correct explanation. Thus, both assertion
and reason are true, but reason is not the correct explanation of the assertion.
Ans. 20. Complex organisms have highly well developed tissue and organ system to perform a
particular function. There is division of labour in the body of complex organisms. Their
body is highly complicated and the tissue and organ system are highly differentiated and
are made up of different kinds of cells. So, it is very difficult for complex organisms to
give rise to new individuals through regeneration, which is seen in simple organisms like
Hydra, Planaria etc.
Ans. 21. (i) (d) adolescence
(ii) (a) ovulation
(iii) (a) I, II and III
(iv) (a) 11 to 13 years
(v) (c) menarche

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 Answers Worksheet - 9
Chapter - 3 [How do Organisms
Reproduce?]
Ans. 1. (d) (iii), (iv).
Ans. 2. (a) Pollen grains, anther, filament.
Ans. 3. (b) I, III, II, V, IV.
Ans. 4. (b) (ii), (iii), (iv)
Ans. 5. A program to regulate the number and spacing of children in a family through the
practice of contraception or other methods of birth control.
Ans. 6. Vas deferens is blocked / Vasectomy in males. Fallopian tube is blocked / Tubectomy in
females.
Ans. 7. (a) After fertilization ovule develops into seeds and ovary into fruit.
(b) Mostly angiosperms show double fertilization.
Ans. 8. (a) There are a number of diseases that are caused by unsafe sexual intercourse. These
diseases are called STDs “Sexually transmitted disease”.
(b) The full form of HIV is the human Immuno Deficiency virus, and the full form of
AIDS is Acquired Immuno Deficiency Syndrome.
(c) The syphilis is a bacterial infection as it is caused by a bacteria named Treponema
pallidum.
(d) No, trichomoniasis is not a bacterial infection as it is caused by a protozoan named
Trichomoniasis vaginalis.
Ans. 9. (a) The testes is the part of the male reproductive system where the formation of
sperms occurs.
(b)  The embryo develops a special structure called placenta. This structure helps in
the transportation of components from the mother’s body to the embryo. Placenta
also prevents the mixing of the mother’s blood with the baby’s blood.
(c) The other name of the oviduct is the fallopian tube.
(d) The process by which the blastocyst gets attached to the lining of the uterus wall is
termed as implantation. It is an important post-fertilization process. The successful
fusion of male and female gamete results in implantation.
Ans. 10. The advantages of sexual reproduction over asexual reproduction are :
(a) Variations are produced due to sexual reproduction which helps in better survival of
offsprings to the changing environment.
(b) More diversity is seen in case of sexual reproduction as compared to asexual
reproduction.
(c) Due to recombination and crossing over in meiosis process during formation of
gametes and as there is mixing of male and female gametes, genetic variations are
seen which is the main cause of evolution.
Ans. 11. (a) In slice 1 number spores will develop as there is lack of moisture.
(b) In slice 2, white spongy mass like structures with black spots will be seen as both
moisture and darkness favours the growth of bread moulds.
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 (3) In slice 3, there will be no formation of spores even though moisture is present
because the low temperature in refrigerator does not favour the growth of spores.
Ans. 12. (a) (i) Oviducts/Fallopian tubes
(ii) Uterus
(iii) Vagina

(b) Condoms prevent the transmission of sexually
transmitted diseases like syphilis, AIDS and are very
convenient and economical to use. So many people prefer
to use condoms. They act as a mechanical barrier to
prevent meeting of sperms and egg. Thus they are an important method to prevent
unwanted pregnancy.
Ans. 13. (a) (i) A hormone is secreted by ovary which causes thickness of inner lining of uterus
and oviduct i.e., it prepares the uterus for proper implantation of embryo. The wall
of uterus gets richly supplied with blood vessels. If implantation occurs, a special
tissue called placenta develop from uterine wall which supplies food, oxygen to
the growing embryo and removes wastes, carbon dioxide from embryo. Placenta
connects uterine wall of mother with embryo.
(ii) If egg is not fertilised the egg disintegrates and the thick lining of uterus starts
shedding off. The egg along with mucus, blood is discharged out through vagina
as menstrual flow.
(b) During copulation sperms get deposited near the cervix of uterus. Sperms swim with
their tail and move forward to uterus. Then they climb up to the oviduct if any egg
would be present one sperm reaches the egg and fuses with it to form zygote. This
process is called fertilization and its site is oviduct. Egg is released by ovary which is
picked up by oviduct. Though an egg may be surrounded by several sperms, only one
sperm enters the egg. After an egg is fertilized with a sperm the entry of other sperms
is prevented by a chemical barrier.
Egg is released by ovary only once in every month by a process called ovulation which
mainly occurs around the day 14th of menstrual cycle. So, it is said that fertilization
can occur once in a month.
. 14. (a) The different types of asexual reproduction seen in living organisms are :
(i) Fission : It is the process in which a unicellular organism splits into two or more
daughter cells. They are mainly of two types—binary fission seen in Amoeba,
Paramecium and multiple fission seen in Plasmodium.
(ii) Fragmentation : It is seen in Spirogyra.
(iii) Regeneration : It is seen in Hydra, Planaria.
(iv) Budding : It is seen in yeast, Hydra.
(v) Spore formation : Here reproduction occurs through formation of spores. Spores
under favorable conditions give rise to new individuals. It is seen in Rhizopus,
Mucor, etc.
(vi) Vegetative propagation : It is mainly seen in plants.
(b) The figure depicts fragmentation process in Spirogyra. In this case organism after
maturation breaks into smaller fragments and each fragment grows into a new
individual. This process is called fragmentation.
Ans. 15. The precautions while studying different parts of embryo of a dicot seed are :
(a) The slide should first be observed under low power magnification compound
microscope and then under high power magnification compound microscope.
(b) The slides should be focused properly.
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Ans. 16. (a) The male gamete must be transferred to the female gamete for fertilization in
flowering plants. The process of transfer of male gamete is pollination. Hence, if
pollination does not take place, fertilization will not occur.
(b)  Complex multicellular organisms cannot give rise to new organism because the
tissue and specialised cell make up the organs in the body. Due to this high degree of
specialization, multicellular organisms cannot reproduce by regeneration of a part of
some tissue.
(c) Vegetative propagation is practised for growing only some types of plants because of
the following reasons:
1. Plants that have lost their capability to produce seeds can be propagated by this
method.
2. It helps to grow plants bearing superior traits, as they are genetically identical to
the parent plant.
3. It is used for growing plants which require a longer time to grow and become
mature.
However, there are certain disadvantages such as:
1. No genetic variations, so less adaptability to the environment.
2. The disease of plants gets transferred to the offsprings.
Ans. 17. Sperms formed in the testes ¾® Epididymis ¾® Vas deference ¾® Urethra ¾® Penis.
Ans. 18. (c) Copper-T is a contraceptive method, which is inserted inside the uterus, it prevents
implantation. It does not prevent sexually transmitted disease. Thus assertion is true,
but reason is false.
Ans. 19. (b) Both the statements are correct, placenta performs both the given functions. But they
are not related to each other. Being an endocrine tissue it releases hormones but does
not help in transport of materials to and from the embryo. Thus, both assertion and
reason are true, but reason is not the correct explanation of the assertion.
Ans. 20. (a) The sperms are known to be the male gametes, and they are produced in the testis.
(b) Penis is the part of the “male reproductive system”. Males use penis for sexual
intercourse. The penis contains a number of blood vessels. These vessels are supplied
with blood. The blood circulation in the penis increases during sexual intercourse.
(c) A duct called epididymis is present in the reproductive part of the males. The newly
formed sperms are stored in this duct. They get matured in this duct.
(d) The seminal vesicles are present in the male reproductive part. It is an exocrine gland
that releases a sugary component in semen.
Ans. 21. (i) (a) Binary fission
(ii) (d) Corals
(iii) (b) A-2, B-1, C-4, D-3, E-5
(iv) (a) Multiple fission in Plasmodium
(v) (d) Fragmentation

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 Answers Worksheet - 10
Chapter - 4 [Heredity]

Ans. 1. (a) Homozygous

Ans. 2. (c) (iii), (iv).
Ans. 3. (d) Combination of x and y chromosome from either of its parents.
Ans. 4. (a) Autosomes do not play any role in the determination of the sex of an individual since
they are alike in both the males and the females and are 22 in pairs.
Ans. 5. Scientific name of man is Homo sapiens and garden pea is Pisum sativum.
Ans. 6. (a) The dihybrid cross experiment that Mendel performed with the pea plants, shows
that traits are inherited independently. In a cross between two plants with two pairs of
contrasting characters, the expression of traits occurs independently.
(b) Mendel further found BY MONOHYBRID CROSS that the phenotypic ratio of 3 : 1
of dominant to actually a genotypic ratio of 1 : 2 : 1 of pure dominant, hybrid and
pure recessive forms traits which remain hidden in F1 generation got expressed in F2
generation. This was later proved in F3 generation.
(c) When an allele affects the phenotype of an organism, then it is a dominant allele. It is
denoted by a capital letter. For example, ‘T’ to express tallness.
Ans. 7. In some animals temperature in which fertilized egg is incubated plays an important role
in determining sex of the new born. Example – turtles, lizards.

Genetically in human sex is determined by sperm. When an X bearing sperm fertilize egg
it will be a girl and when a Y bearing sperm fertilise an egg it will be a boy.
Ans. 8. (a) The modern name of these factors is genes.
(b) Genetics is the branch of biology that deals with the study of heredity and variations.
Ans. 9. The child will be a male because the sex chromosome that the child inherits from his or
her father will determine the sex as mother has only X chromosome. Here as the child
inherits Y chromosome from his father so he will be a male (XY).
Ans. 10. When Mendel crossed pure tall (TT) pea plants with pure dwarf (tt) pea plants, in
F1 generation he found that all pea plants were tall (Tt). There were no dwarf plants
produced in F1 generation. When he self-pollinated these F1 plants, in F2 generation he
obtained tall and dwarf plants in the ratio 3 : 1. Thus, as three-fourth of the plant in F2
generation are tall and one-fourth is dwarf so tall is a dominant trait whereas dwarf is a
recessive trait [which expressed itself only in homozygous condition]. The dwarf trait was
inherited in F1 generation but it does not get expressed, it remains suppressed in presence
of dominant trait (tall).

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Ans. 11. There are 50% chances that a girl may be born and 50% chances that a boy may be born. It
can be explained as follows:
Most human chromosomes have a maternal copy and a paternal copy. We have 22 such
chromosomes. One pair of chromosomes called sex chromosomes is odd in not always
being a perfect pair. Women have a perfect pair of sex chromosomes, both called X. (XX).
But men have a mismatched pair of sex chromosomes in which one is normal sized – X
chromosome while the other is a short one called Y chromosome. (XY).
A child receives one chromosome from mother which is essentially X chromosome.
A child who inherits an X chromosome from her father will be a girl, and one who
inherits a Y chromosome from him will be a boy.
Ans. 12. Absence of tail in mouse after surgical removal and low weight of a starving beetle
cannot be passed on to the progeny as they are acquired traits and they do not cause
any change in the DNA of germ cells. These changes occur in somatic tissues hence are
not transmitted to their progeny. Whereas a rudimentary eye of Planaria is controlled
by specific genes present in germ cells which can be transmitted from generation to
generation.
Ans. 13. Genes are a specific sequence on nucleotides on chromosome which encodes a particular
protein which express in form of a particular trait in the body. Each gene has two
alternative forms for a particular character. These alternative forms are called alleles,
one is dominant allele and other is recessive allele. For example – Height of a plant,
plant height depends on the amount of hormones synthesized. The amount of hormones
synthesized depends upon the efficiency of the process for making it. If the protein
needed for this process is synthesized and works efficiently plant would be tall. On the
other hand if the gene is altered, the protein synthesized will be less efficient and hence
hormones produced would be less and plant would be dwarf.
Ans. 14. The basic features of the mechanism of inheritance are :
(i) Traits are controlled by genes.
(ii) Genes are present on chromosomes.
(iii) Each gene controls one character.
(iv) There may be two or more forms of a gene.
(v) One form may be dominant over the other.
(vi) An individual possesses two forms of genes which may be similar or dissimilar.

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 (vii) The two forms of gene separate at the time of gamete formation.
(viii) The two forms of gene are brought together in a zygote after fertilization.
Ans. 15.

Gametes ®
RY Ry rY ry
¯
RY RRYY RRYy RrYY RrYy
Ry RRYy RRyy RrYy Rryy
rY RrYY RrYy rrYY rrYy
ry RrYy Rryy rrYy rryy
Round-yellow, round-green, wrinkled-yellow, wrinkled-green in the ratio of 9 : 3 : 3 : 1 are
produced in F2 generations.
New characters round-green and wrinkled-yellow are produced because when pure
round-yellow pea plants are crossed with pure wrinkled-green pea plants the inheritance
of one pair of character is independent of other pair i.e., the inheritance of character of
round seed is not linked with yellow seed or the inheritance of wrinkled seed is not
linked with green seed. The contrasting traits segregate and inherits independently and
results in formation of new combination of characters.
Ans. 16. The findings of Mendel are known as Mendel’s Laws of Inheritance.
Mendel derived three laws from his experiment :
Law of dominance : It states that out of a pair of contrasting characters present together,
only one expresses which is called dominant character and the other which remains
suppressed and unexpressed is called recessive character.
Law of segregation : During formation of gamete the two members of a pair of factors
separate. These factors get separate into different gametes.
Law of independent assortment : When there are two pairs of contrasting characters,
the distribution of the members of one pair into the gametes is independent of the
distribution of the other pair.
Ans. 17. Experiment with garden pea plants (Pisum sativum), Austrian monk Gregor Johann
Mendel (1822-1884) choose to experiment because they possessed four important qualities
:
(i) Peas had been shown to be true-breeding (all offspring will have the same
characteristic generation after generation).
(ii) Peas exhibit a variety of contrasting traits (purple vs. white flowers; round vs.
wrinkled seeds).

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 (iii) The shape of the pea flower protected it from foreign pollen. Peas usually reproduce
by self-pollination, in which pollen produced by a flower fertilizes eggs in the same
flower.
(iv) Pea plants grow quickly and do not require much space.
The traits that Mendel studied are listed below:
Form of ripe seed (R) – smooth or wrinkled
Color of seed albumen (Y) – yellow or green
Color of flower (P) – purple or white
Form of ripe pods (I) – inflated or constricted
Color of unripe pods (G) – green or yellow
Position of flowers (A) – axial or terminal
Length of stem (T) – tall or dwarf
Ans. 18. (a) The pea plant which Mendel choose for conducting experiments, is most ideal for
controlled breeding, since it can easily be subjected to cross pollination. He identified
very clear contrasting characters in the pea plants. Thus, both assertion and reason are
true and reason is the correct explanation of the assertion.
Ans. 19. (c) The law of independent assortment states that two factors of each character assort or
separate independent of the factors of other characters at the time of gamete formation
and get randomly rearranged in the offspring producing both parental and new
combinations of traits. The principle of law of independent assortment is applicable to
only those factors or genes which are either located distantly on the same chromosome
or occur on different chromosomes. Actually, a chromosome bears hundreds of genes.
All the genes of factors present on a chromosome are inherited together except when
crossing overtakes place. Thus, assertion is true but reason is false.
So, the correct answer is 'Assertion is correct but Reason is incorrect'.
Ans. 20. (a) The process by which the sex of a newborn organism is detected is called sex
determination.
(b) The males have two sex chromosomes which are X and Y.
(c) The sex chromosomes in the females are X and X.
(d) Yes, the father is solely responsible for the sex of the child because the mother gives
only the X chromosome to the child. It is the father that gives either the X or Y
chromosome to the child. In case, the child receives the X chromosome from the father,
then it has XX chromosome, and it develops into a female child. However, if the father
gives Y chromosome, then the child develops into a male as it gets XY chromosome.
Ans. 21. (a) Bar diagram shows the proportion of females in the population over a decade.
(b) 1 : 1 should be the sex ratio or the male to female ratio at a given point of time.
(c) Female foeticide is the main reason to this trend showing deviation from the expected
sex ratio.
(d) Banning sex tests of unborn baby; increasing awareness and education will help to
stop such trends.

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 Answers Worksheet - 11
Chapter - 4 [Heredity]

Ans. 1. (a) Copies of the same chromosome.

Ans. 2. (c) Size of body.
Ans. 3. (c) Growth hormones under the influence of the enzymes coded by a gene.
Ans. 4. (a) In individuals of a given species, a specific gene is located on a particular
chromosome.
Ans. 5. Ova or eggs are of one kind only. These contain 22 autosomes and a single X chromosome.
Sperms are of two kinds (i) having 22 autosomes and one X chromosome, or (ii) having 22
autosomes and a Y chromosome.
Ans. 6. If the male have 24 chromosomes then the female will also have 24 chromosomes and the
zygote will have 48 chromosomes.
Ans. 7. There are 23 pairs of chromosomes present in human beings. One pair is sex chromosome.
They are XX and XY. So, there are two types of sex chromosomes.
Ans. 8. The other member of the pair is dominant and masks the effect of the recessive gene. In
this way, a person can be normal for a trait even when carrying one defective gene for that
trait.
Ans. 9. (a) No, it is not correct for the insurance company to deny medical insurance to Satyam
as denial of insurance will put Satyam and his family under high pressure both
financially and mentally. Genetic test reveals that he is under high risk of getting
heart disease so he can take precautions by taking medicines to prevent this disease.
So insurance company should provide him insurance for this.
(b) No, tests for genetic diseases should not be banned instead it is a great boon for
people to save their lives.
(c) Government should enforce laws to keep genetic tests report confidential without
disclosing them to others. No people should be discriminated based on genetic
diseases in office, schools, institution or any work places. Insurance company should
provide insurance for all genetic diseases.
Ans. 10. No, because the blood group is defined by a pair of genes, the information is insufficient.
one came from the mother, while the other came from the father. In this situation, the
youngster received to O blood group gene from both his mother and father.
Ans. 11. In human beings, there are two types of sex chromosome X and Y; female have XX
chromosome whereas male have XY chromosome. Females produce eggs which carry
only X chromosomes but males contain half of the sperms with X chromosomes and other
half with Y chromosomes. During fertilization when X carrying sperms fuse with an egg
which contains X chromosome the offspring will be a female (XX). But when Y bearing
sperms fuses with an egg (X) the offspring will be male (XY). Thus, the sex of a child is
determined by the type of sex chromosome X or Y received by the male gamete.
Ans. 12. Females have only one type of sex chromosomes i.e., X chromosome but a male has two

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 types of sex chromosomes X and Y chromosomes. So,
a woman will produce eggs having X chromosomes
only but a man will produce 50% sperms carrying
X chromosomes and rest 50% sperms carrying Y
chromosomes. So, the sex of a child is determined
whether X or Y containing sperm fertilize X containing
egg. In this case every time X containing sperm fertilize an
egg so the woman has only four daughters and no son.

Ans. 13. Inherited traits Aquired traits
A trait (or characteristic) of an organism A trait (or characteristic) of an organism
which is ‘not inherited’ but develops in which is caused by a change in its genes
response to the environment is called an (or DNA) is called an inherited trait.
acquired trait. Inherited traits can be passed on to the
progeny of the organism because they
have produced changes in the genes (or
DNA) of the organism.
For example, if a group of mice are For example, skin color in human beings.
normally bred, all their progeny will have
tails. Now, if the tails of these mice are cut
by surgery in each generation, tail-less mice
will not be produced. This is so because
removal of tail is an acquired character.
Ans. 14. Blood group A can be represented as IAIA or IA IO which is the father’s blood group. Blood
group AB can be represented as IA IB, which is mother’s blood group. So, the possible
blood group of their children can be A, AB or B.
This can be explained from the Punnett square given below :
1. Or 2.

Children can have blood group A, AB. Children can have blood group A, AB or B.
So, children can have A, AB or B blood groups.
Ans. 15. (a) (i) Color of stem in F1 progeny :
Green stemmed Brown stemmed
rose plant rose plant

Parents GG × gg

Gametes G g

F1 progeny Gg
Green stemmed rose plant
The color in the F1 progeny is green stemmed as green stem color is dominant.

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 (ii) F1 progeny on self pollination :

F2 generation Green stemmed: Brown stemmed 14 or 25% of F2 progeny are brown
stemmed rose plant.
(iii) Ratio of GG and Gg in F2 progeny:
Genotype of F2 progeny – GG : Gg 1 : 2
(b) This is a monohybrid cross. This shows that out of two contrasting traits only one
dominant trait appears in F1 generation and the trait which does not express is
recessive. On selfing the F1 plants, both the traits appear in next generation but in a
definite proportion.
Ans. 16. (a) 
When Mendel crossed pure tall pea plants with pure dwarf pea plants in F1
generation only tall plants were produced. When these F1 plants were self-pollinated
in F2 generation both tall and dwarf plants were produced in the ratio of 3 : 1. In F1
generation only tall plants were found so it showed that tall is a dominant character.
In F2 generation dwarf plants appeared which shows that dwarf is a recessive trait
which express only in recessive condition.
Parental generation plant ® Pure tall plant × Pure dwarf plant
TT tt
Gametes ® T t
F1 generation ® Tt (Tall)

Tt × Tt
Gametes ® T, t T, t
F2 generation ® TT(tall), Tt(tall), Tt (tall), tt (dwarf )
(b) When Mendel crossed pure pea plants with round and yellow seeds with pure plants
with wrinkled and green seeds, in F1 generation all pea plants with round and yellow
seeds were produced. This shows that round and yellow are dominant characters
whereas green and wrinkled are recessive characters. Again when these F1 plants
were crossed, round and yellow pea plants as well as green and wrinkled seeds pea
plants were produced. But in addition to these two new characters were produced
i.e., round and green and wrinkled and yellow seeds pea plants were produced.
 This shows that two pair of characters combine in F1 generation but they get
separated and behave independently in F2 generation.

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 Gametes ®
RY Ry rY ry
¯
RY RRYY RRYy RrYY RrYy
Ry RRYy RRyy RrYy Rryy
rY RrYY RrYy rrYY rrYy
ry RrYy Rryy rrYy rryy
Round-yellow, round-green, wrinkled-yellow, wrinkled-green – 9 : 3 : 3 : 1
Ans. 17. The sex chromosome in human female is homomorphic i.e., they contain same
chromosome XX. During meiosis process at the time of gamete formation all egg cell will
get one copy of X chromosome, hence all the gametes formed in human females have an
X-chromosome.
Ans. 18. (a) Inheritance is the process by which characters are passed on from parent to progeny.
This inheritance leads to heredity. Heredity, the sum of all biological process by
which particular characteristics are transmitted from parents to their offspring, the
set of genes that an offspring inherits from both parents, a combination of the genetic
material of each, is called the organism's genotype. Thus, both assertion and reason
are true and reason is correct explanation of the assertion.
Ans. 19. (c) Genes inherited from the parents decide the sex of a child. A child who inherits the
'X' chromosome from his father would be a girl (XX), while a child who inherits a 'Y'
chromosome from the father would be a boy (XY). Thus, assertion is true but reason is
false.
Ans. 20. (a) Gametes are haploid cells. Egg and sperm cells have just 23 chromosomes each. That's
half as many chromosomes as regular cells. The fusion of two haploid cells results in the
formation of a diploid cell. Therefore, zygote is a diploid cell with 46 chromosomes.
(b) Some animals (reptiles) rely entirely on environmental cues for sex determination. In
some reptiles, the temperature at which fertilized eggs are kept determines whether the
developing animal in the egg is male or female. Ex- lizard. In some animals like the snail,
an individual can change sex under different stress and environmental conditions.
(c) The sex of a newborn child is purely and completely a matter of chance and none of
the parent i.e. mother and father may be considered answerable for it. The statement in
question is justified and can be proved by the process of fertilisation:

Father XY Mother XX

Spermatozoa Ova

X Y X X

XX XX XY XY

Female 50% Male 50%

Ans. 21. (i) (d) A are dwarf and B are tall.

(ii) (c) (i) Brown and (ii) Brown.
(iii) (b) round and yellow.
(iv) (b) Dihybrid cross.
(v) (d) Equal chance of acquiring blood group A or blood group O.

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 Answers Worksheet - 12
Chapter - 4 [Heredity]

Ans. 1. (c) Dominant trait, Inherited trait

Ans. 2. (b) 3 : 1
Ans. 3. (a) Autosomes
Ans. 4. (a) 1
Ans. 5. In F1 progeny it will lead to production of pea plants with violet flowers as the trait violet
color flowers are dominant over white color flowers in pea plants.
Ans. 6. Monohybrid Dihybrid
Monohybrid involves cross between Dihybrid involves cross between parent , which
parents, with the first in only one pair differ in two pair of contrasting characters.
of contrasting characters.
For example, the cross between tall and For example, the cross between pea plants hav-
dwarf pea plant. ing yellow wrinkled seed with those having
green round seeds.
Ans. 7. (a) It depicts monohybrid cross.
(b) In F1 generation all pea plants with yellow seeds will be produced whereas in F2
generation pea plants with yellow and green seeds in the ratio 3 : 1 will be produced.
(c)

Ans. 8. (a) Genotype Phenotype

The genotype is the genetic makeup The phenotype is the physical appearance due
of the trait present in the organism. to the presence of a trait.

For example, TT or Tt is the geno- For example, the cross between pea plants hav-
type for the trait height. ing yellow wrinkled seed with those having
green round seeds.

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 (b) Genotype Phenotype
The group of features, traits and charac- The phenotype is the physical appearance
teristics that form the individual nature due to the presence of a trait.
of some person or thing.
For example, TT or Tt is the genotype for Trait is distinguishing characteristics equal-
the trait height. ity, especially of one's personal nature.
Ans. 9. Law of independent assortment governs this expression which states that inheritance
of factors controlling a particular trait in an organism are independent of each other
i.e., during the time of reproduction two pairs of factors of each of the two traits in a
dihybrid cross segregate independently during gamete formation and randomly formed
combinations in F2 generations.
Ans. 10. When Mendel crossed pure tall (TT) pea plants with pure dwarf (tt) pea plants, in
F1 generation he found that all pea plants were tall (Tt). There were no dwarf plants
produced in F1 generation. When he self-pollinated these F1 plants, in F2 generation he
obtained tall and dwarf plants in the ratio 3 : 1. Thus as three-fourths of the plant in F2
generation are tall and one-fourth is dwarf so tall is a dominant trait whereas dwarf is a
recessive trait [which expressed itself only in homozygous condition]. So he concluded
that for a particular trait [here in this example height of the plant] it may be dominant or
recessive.
Parental Generation Pure Tall Pea Plant x Pure Dwarf Pea Plant
TT tt

Gametes T x t

Tt
[Tall]
F1 Generation

Tt [Tall] Tt [Tall]

Gametes
T t T t

F2 Generation

TT Tt Tt tt
[Tall] [Tall] [Tall] [Dwarf]
Genotype : 1 : 2 : 1
Phenotype : 3 : 1

Ans. 11. (a) The trait which gets expressed in F1 generation is called dominant trait. It gets
expressed in both homozygous and heterozygous condition. The trait which remains
suppressed in F1 generation, which cannot express itself in presence of dominant
trait is called recessive trait and it gets expressed only when present in homozygous
condition.
(b) Genes are a specific sequence on chromosome which encodes a particular protein
which express in form of a particular trait in the body. Each gene has two alternative
forms for a particular character. These alternative forms are called alleles, one
is dominant allele and other is recessive allele. For example – Height of a plant,
which depends on the amount of hormones synthesized. The amount of hormones
synthesized depends upon the efficiency of the process for making it. If the protein
needed for this process is synthesized and works efficiently, plant would be tall. On
the other hand if the gene is altered, the protein synthesized will be less efficient and
hence hormones produced would be less and plant would be dwarf.

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Ans. 12. Law of Dominance : As tall is dominant over dwarf trait so in F1 generation tall character
will be expressed as recessive trait gets expressed only in homozygous condition.
Ans. 13. (a) Tt
(b) Because only Dominant trait (Tall) is expressed in F1 generation / Tallness is dominant
over recessive short trait.
(c) F2 generation – Tall : short
3:1
Ans. 14. (a) Tall – Dwarf (Height of plant)
White – Purple (Color of flower)
(b) Genotype Phenotype
Dominant Trait are expressed even if Recessive Trait are Whose expression is
one copy of dominant trait exists. suppressed by a dominant gene/ Expressed
when two copies of recessive traits are pres-
ent.
(c) 9 : 3 : 3 : 1.
Ans. 15. This determines which traits are passed from the parent to the offspring. Successful
traits are inherited more often and change species over time. Changes in traits allow an
organism to adapt to a particular environment and increase survival.
Ans. 16. (a)

(b) Mendel carried out experiment with two traits to study the independent assortment of
characters during inheritance.
(c) In F1 generation though both the traits were inherited but only dominant traits [i.e.,
round, yellow characters] are expressed while the recessive traits [wrinkled, green] are
not expressed. But in F2 generation both dominant and recessive traits were expressed
in the ratio 9 : 3 : 3 : 1.
Ans. 17. Change in non-reproductive tissues cannot be passed on to the DNA of the germ cells,
these are acquired traits. Therefore, the experiences of an individual during its lifetime
cannot be passed on to its progeny and cannot direct evolution.
Ans. 18. (a) The pea plant which Mendel chose for conducting experiments, is most ideal for
controlled breeding, since it can easily be subjected to cross pollination. He identified

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 very clear contrasting characters in the pea plants. Thus, both assertion and reason are
true and reason is the correct explanation of the assertion.
Ans. 19. (c) Mendel took two contradicting traits together for crossing i.e. color and shape of
seeds. He chose a round yellow seed and a wrinkled green seed and crossed them.
He obtained only round yellow seeds in the F1 generation. Then, F1 progeny was
self-pollinated, which gave four different combinations of seeds i.e. round-yellow,
wrinkled-yellow, round green and wrinkled green seeds in the F2 generation. So,
assertion is true but reason is false.
Ans. 20. (a) According to the law of dominance, the parent contains two alleles, out of which one
is the dominant allele while the other is the recessive allele.
(b) The allele that expresses itself and reduces the expression of other alleles is termed as
the dominant allele.
Ans. 21. (a) Free ear lobe is dominant because it is found in a large majority of the population.
(b) No. It is not sex linked. As per the data of the family as well as the class, it is indicated
that free ear lobe is present in males as well as in females.
(c) Father – Ff (free ear lobe), Mother – Ff (free ear lobe), Rahul – ff (attached ear lobe)
and Nisha – Ff (free ear lobe)

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 Progress Check - 2

Ans. 1. (d) Rose, root.

Ans. 2. (c) (i), (ii)
Ans. 3. (a) Gametes, zygote, embryo, seedling.
Ans. 4. (b) Halving of chromosomes during gamete formation.
Ans. 5. (a) Genetics. (b) Heredity
Ans. 6. (a) Parturition.
(b) Oviducts/Fallopian tubes.
Ans. 7. (a) Anthers (b) Ovary (c) Ovules (d) Pollens.
Ans. 8. No, this information is not enough to find out which blood group is dominant. Blood
group A can be represented as IAIA or IA IO, which is the father’s blood group. Blood
group O is represented as IOIO which is the mother’s blood group. The blood group of
daughter is also O which might be inherited from her mother or father so it is difficult to
assume which blood group is dominant.
Ans. 9. (a) Sepals/calyx and petals/corolla
(b) Genotype Phenotype
Transfer of pollen grain from anther to Transfer of pollen grain from anther to stig-
stigma in the same flower or another ma of one flower to another of two different
flower of the same plant is called self plants is called cross pollination.
pollination.
Significance.
1. Necessary for seed formation.
2. Stimulates development of fruits.
3. Cross pollination brings about genetic variation
4. Leads to fertilization.
Ans. 10. During DNA replication two identical replicas of DNA are produced from the original
DNA but sometimes during replication there are changes in base sequences due to
mutation or due to minor changes in DNA replication. Thus, at times newly formed DNA
copies may not be identical.
Ans. 11. DNA is the hereditary material. It stores the blueprint in the genes. Genes control
synthesis of proteins. These proteins act as enzymes which control biochemical reactions
of the body. Genes are responsible for transmitting characters from parents to offspring.
Before transmitting characters from parents to offspring prior to cell division, DNA makes
its copies by replication. Hence, DNA contains the blueprint of the next generation.
Ans. 12. (a) The two bacterial diseases that are caused due to unprotected sex are gonorrhea and
syphilis.
(b) The pill helps in preventing pregnancy as it prevents the release of the ovum, by
changing the hormonal balance.

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 (c) Vasectomy is the surgical process by which the vas deferens is cut. This prevents the
sperms from reaching the ejaculatory duct.
(d) The common side-effects of using contraceptive pills are irritation, nausea and mood
swings.
Ans. 13. Human beings contain 23 pairs of chromosomes and 22 pairs are autosomes and one
pair sex chromosomes. During meiosis process gametes are formed in sex cells where the
chromosome number is halved(n). At the time of fertilization when male gamete fuses
with female gamete the diploid number (2n) is restored back in zygote. Thus half of the
chromosomes come from father and other half from mother. In this way meiosis process
ensured equal genetic contribution of male and female parents in the progeny.
Ans. 14. (a) Green color (b) 25% (c) 3 : 1

Ans. 15. (a) The figure indicates fertilization process in flowering plant.
(b) A – Pollen grains, B – Stigma, C – Male gametes, D – Style, E – Pollen tube, F – Ovule,
G – Ovary, H – Embryo sac.
(c) Stigma is the part of carpel which receives pollen grains during pollination.
Pollen tube contains the male gamete which passes through the style and finally
reaches the ovary. It carries the male gametes towards female gametes for fertilization.
Ans. 16. (a) Common name is bread mould and scientific name is Rhizopus stolonifer.
(b) Spores of Rhizopus are present in air and when they landed on suitable substratum
like moist slice of bread, under favorable conditions like availability of suitable
temperature, moisture, nutrients the spores germinates to produce new individuals.
(c) Fine thread like projections are called hyphae and bulb like structures are called
sporangia.
(d) It is called reproduction by spore formation and bacteria reproduce by this method.
(e) Sporangia contain spores in them which are responsible for reproduction.
Ans. 17. Blood group AB has two alleles A and B in the people of all communities.
Ans. 18. (b) Smaller Y chromosome does not decide the gender of the child its presence is
important not the size. Thus, both assertion and reason are true, but reason is not the
correct explanation of the assertion.
Ans. 19. (d) Gene B is responsible for black eyes and is dominant, whereas gene b is responsible
for brown eyes and is recessive. If an individual has a genotype of BB or Bb, they will
have black eyes, and if the genotype is bb, they will have brown eyes. Thus, assertion
is false but reason is true.

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Ans. 20. Yes, the chromosome number of zygote, embryonal cells and adult of a particular
organism is always constant. Because zygote is diploid and it undergoes mitotic divisions
to form embryonal cells and finally adult and during mitosis the chromosome number
remains constant.
Ans. 21. (i) (d) Both (a) and (b)
(ii) (a) Uterus
(iii) (d) About seven days
(iv) (c) Determine disease of the embryo
(v) (b) Flagellum
Ans. 22. (i) (a) In human beings, the statistical probability of getting either a male or female
child is 50:50.
(ii) (b) X chromosome from mother will also show its effect
(iii) (d) Father and mother both having blood group O could have a child of blood
group AB
(iv) (d) All of these
(v) (b) Mutation

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 Answers Worksheet - 13
Chapter — 5 [Our Environment]

Ans. 1. (d) All of the above

Ans. 2. (d) The population of tiger decreases and the population of grass increases
Ans. 3. (b) Green plants get their food from organic compounds.
Ans. 4. (d) Characteristics will remain the same even if protein changes.
Ans. 5. (i) Plants capture only about 1% of the solar energy that falls on them and use it for
photosynthesis.
(ii) On average, only about 10 percent of energy stored as biomass in a trophic level is passed
from one level to the next. This is known as “10 percent rule” and it limits the number of
trophic levels an ecosystem can support.
Ans. 6. Use of air conditioners, refrigerators etc., that contain CFCs, when released into
atmosphere leads to depletion of ozone layer.
Ans. 7. The various steps in a food chain or ecological pyramid, at which the transfer of food (or
energy) takes place from one organism to another organism is known as trophic levels. Based
on the source of their nutrition or food, organisms occupy a specific place in the food chain.
Organisms in food webs are grouped into categories called trophic levels, these levels are
divided into producers (first trophic level), consumers, and decomposers (last trophic level).
There is only 10% flow of energy from one trophic level to the next higher level. The loss of
energy at each step is so great that very little usable remains after four or five trophic levels.
Hence only 4 to 5 trophic levels are present in each food chain.
Ans. 8. We can help in reducing the problem of waste disposal by following two methods :
(a) We should try to reuse materials so that we can minimize the production of wastes and
also its disposal.
(b) We should try to separate biodegradable and non-biodegradable wastes and dispose
them separately, as biodegradable wastes can be converted into compost and can be
used as manure in agricultural fields or kitchen gardens. Non-biodegradable wastes
can be recycled in recycling units.
Ans. 9.
Food chain Food web
The sequential interlinking of organisms It is a network of food chains interlinking
where energy in form of food is transferred many organisms at different trophic levels
from the producers through a series of which eat or being eaten and thus formed a
consumers is a food chain. number of feeding connections.
A food chain shows one path how energy A food web shows many paths i.e., it is a
in form of food flows from producers to network of food chains where an organism
consumers. eat several types of organisms or eaten by
many different organisms.
Ans. 10. Ozone layer is present in stratosphere which prevents harmful UV rays of sun from
entering the surface of earth. So, damage to this layer will cause a serious effect on human
body. UV rays can cause skin cancer, genetic mutation, cataract of eyes etc.
Two steps to limit this damage are :

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 (a) We should restrict the use of CFCs which is the main cause of depletion of ozone layer. It
is used in ACs, refrigerators, aerosol sprays. Instead we should use some other substances
like HFC instead of CFCs in these equipments. Alternate technology will be developed to
replace the use of CFCs.
(b) Limited use of supersonic planes and control over large scale nuclear explosions.
Ans. 11.
Biodegradable substances Non-biodegradable substances
These substances are easily degradable in These substances are not degraded in
nature by the action of microbes like bacteria nature by the action of microbes.
and fungi.
These substances remain for a short period They persist for longer period of time in
of time in environment. the environment.
Examples : Peels of vegetables, fruits, paper Examples : Plastic, metals, glass objects etc.
etc.
Ans. 12. (a) The effluents of industries containing non-biodegradable wastes get mixed with water
bodies. These non-biodegradable toxic wastes get accumulated in the body of fishes
and when people consumed these fishes they fall ill.
(b) Effluents should be properly treated before letting them into water bodies.
(c) This phenomenon is called bio-magnification.
Ans. 13. (a) (i) If all rats will be removed from the food chain the amount of grass will increase
and the amount of snakes will decrease as they will not get their food and will die
of starvation. Similarly, the population of hawk will also be affected as they will
not get their food i.e., snakes.
(ii) If all snakes are removed then hawks will not get their food and will die of
starvation. The number of rat population will also increase.
(b) (i) Grass will transfer the maximum amount of energy.
(ii) Hawk will receive the minimum amount of energy.
(c)

Ans. 14. The energy from sun flows through various trophic levels. The food and energy are
transferred from producers to herbivores and from herbivores to carnivores, through the
food chain.
First Step : The green plants trap solar energy with the help of green pigment called
chlorophyll which converts the sunlight energy into chemical energy. This gets stored as
carbohydrates in the plants. About 1% of the sun's energy falling on the leaves is used
by the plants in the process of photosynthesis and stored as chemical energy of food.
The plants utilize the stored energy for their metabolic activities like respiration and
growth. Some of the energy is not utilized and it is released as unusable heat into the
environment.
Second Step : The plants are eaten up by herbivores and the chemical energy of plants is
transferred to them. The herbivores utilize this energy for various metabolic activities and
release unused energy as heat energy to the environment.

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Third Step : The herbivores
are eaten up by carnivores. The
chemical energy stored in the flesh
of herbivores is transferred to the
carnivores and they utilise this
energy for their metabolic activities
like respiration and growth and
some of the energy which remains
unutilized, is released into the
environment. This process of
transfer of energy is repeated with
large carnivores and so on.
Ans. 15. (a) Decomposers are the microbes
that act upon dead and
decaying organisms to convert them into simpler forms. These simple substances
get mixed up in the soil and are used as nutrients by the producers. From producers
it goes to consumers and so on. Thus, there is recycle of matter which is done by
decomposers that maintain balance in the ecosystem.
Dead plants and animals will get accumulated in the ecosystem as there would be no
decomposers to decompose them. But in absence of decomposers this whole process
would not occur and the dead organisms will get accumulated in the ecosystem
causing pollution. Thus, the existence of decomposers is essential in a biosphere.
(b) The flow of energy in an ecosystem is as follows :
Producers ® Primary consumers ® Secondary consumers ® Tertiary consumers
® Quaternary consumers.
The flow of energy is from one trophic level to the next at the rate of 10% according to
Lindemann Ten percent law. So, at each trophic level the energy goes on decreasing.
So, it is impossible to revert back. The energy captured by the producers cannot be
reverted back to the sun. Similarly, the energy obtained by primary consumers cannot
come back to producers and so on. Primary consumers will eat producers but the
reverse cannot be possible. Due to these above reasons the flow of energy in a food
chain is unidirectional.
Ans. 16. (a) (i) Use of disposable items like paper plates, plastic cups in parties.
(ii) Use of various colored polythenes for gift wrappings.
Instead of polythene we can use colored papers for gift wrapping. We can reuse them to
reduce waste.
(b) The peacock will have maximum concentration of harmful chemicals in its body as the
accumulation of harmful chemicals which are non-biodegradable increases at every
trophic level. This phenomenon of increase in concentration of harmful chemicals at every
trophic level is called bio-magnification. Since peacock are placed at top of this food chain
so it will have maximum concentration of the harmful chemicals in its body.
Biological Magnification is the process in which a harmful chemical enters the food chain
and gets concentrated at each trophic level.
(c) The concentration of chemicals goes on increasing at different trophic levels. It is
maximum at higher trophic levels since human beings occupy the top level in a food
chain so there is maximum concentration of toxic substances in our body i.e., bio-
magnification level is maximum and according to 10% law very less amount of energy
is available to humans.

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Ans. 17. The fish would need a free space for swimming, water, oxygen and food. Thus, she need a
good aquarium tank, oxygen can be provided through an oxygen pump (aerator) and fish
food is available in the market.
Water parameters for nitrate, nitrite, ammonia and pH levels are to be maintained. To
condition water properly, use a de-chlorinating and biological aquarium supplement. It is
recommended to change 25 percent of the aquarium water at least once a month. This will
help maintain a clean and healthy tank, plus it keeps nitrate concentrations at a safe level.
Overcrowding can lead to low oxygen levels in the water. Another crisis of overcrowding
includes excess waste, which clogs the filter and degrades the aquarium water.
Ans. 18. (a) Bio-magnification is the increase in concentration of toxins up the food chain.
Chemicals and toxins accumulate more and more as we move up the food chain
because they do not get broken down in the body. Anything that gets into biological
tissue, that is not normally there, has the potential to accumulate and magnify as it
moves up the food chain. Thus, both assertion and reason are true and reason is the
correct explanation of the assertion.
Ans. 19. (c) Biodegradable substances result in the formation of compost and natural
replenishment. It is due to breakdown of complex organic substances into simple
organic substance. Thus, assertion is true but reason is false.
Ans. 20. (a) Ozone layer is found in stratosphere.
(b) Ozone layer prevents the harmful UV rays of sun from entering earth‘s surface.
(c) Various ozone depleting substances like CFCs cause a great damage to ozone layer.
(d) The harmful UV rays from sun can easily pass through this layer and cause various
genetic disorders, mutations, cancer, eye diseases etc., in humans. UV rays also affect
plants and animals.
Ans. 21. (i) (a) 1 percent
(ii) (d) 100 J
(iii) (b) Ecosystem
(iv) (a) Frog : Lizard
(v) (b) man

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 Answers Worksheet - 14
Chapter - 5 [Our Environment]
Ans. 1. (d) Mice and Rabbit
Ans. 2. (a) Food web.
Ans. 3. (d) (ii), (iv).
Ans. 4. (d) 5000 kJ.
Ans. 5. Phytoplanktons ® Zooplanktons ® Small fish ® Large fish
Ans. 6. (a) Global warming. (b) Food Chain.
Ans. 7. (i) Photo-dissociation of ozone and generation of ozone are the two reactions which are in
equilibrium thereby maintaining steady concentration of ozone in the stratosphere.
(ii) Ultraviolet radiations from sun are being absorbed by the ozone for the occurrence of
above two reactions.
Ans. 8. Kulhads are made from the top fertile layer of soil. Use of this soil to make kulhads on a
large scale would lead to loss of fertile top soil. This fertile top soil is of great use for the
growth of plants as it contains many useful nutrients. Hence, kulhads have been banned
for serving tea on platforms. Nowadays disposable paper cups are used in trains and
platforms.
Ans. 9. Plastic bags are non-biodegradable wastes. When burnt they release very poisonous gases
which have serious effects on our body. Plastic bags block drainage system leading to
overflow of drainage. When buried in soil, the fertility of soil is reduced. So, the uses of
plastic bags are banned in many places.
Instead of plastic bags we can use cloth bags, paper bags or jute bags for shopping.
Ans. 10. Ozone is damaging as it is a very poisonous gas. Its beneficial effect is that it acts as a
protective layer for the surface of earth by preventing harmful UV rays of the sun to reach
earth’s surface.
CFC is the main agent for depletion of ozone, by preventing the use of CFCs we can
protect the ozone layer from being damaged.
Ans. 11. The characteristics of energy transfer in biosphere are :
(a) The ultimate source of energy is sun and is converted from one form to another.
(b) Energy gets continuously transferred through food chain and energy flow is
unidirectional.
(c) There is loss of some energy during transfer from one trophic level to the next.
(d) Only 10% of energy is transferred from one trophic level to the next. The solar energy
trapped by producers does not revert back to the sun.
(e) At each trophic level, some of the energy is utilized by organisms, rest is lost to
environment and only 10% is available to the next trophic level.
Ans. 12. An energy pyramid is a graphical representation of the flow of energy from the
producers through the various consumers. It shows the amount of energy available and
the loss of useful energy at each step of the food chain in an ecosystem. As the energy
gets transferred from lower trophic level to the higher one, there is a loss of large amount

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 of energy due to metabolism and as heat. As a result very little energy (i.e., 10%) gets
transferred to the next level. So, the trophic level at the base has maximum energy and
that at the top has the least amount of energy. Hence energy pyramid is broader at the
base and narrower at the top.
Ans. 13. Yes, the impact of removing all the organisms in a trophic level will be different for
different trophic levels. For example – If all producers will be removed then all herbivores
will die of starvation. The various categories of carnivores which depend on herbivores
for food will also be affected. Similarly, if we will remove all organisms of higher trophic
level, the numbers of organisms in lower trophic level will increases thus creating
imbalance in an ecosystem. So, if organisms of any trophic level would be removed it will
cause damage to the ecosystem.
Ans. 14. (a) (i) The two ways in which biodegradable substances would affect the environment
are :
1. Decomposition of biodegradable substances results in production of foul smell.
2. The area where biodegradable wastes are accumulated serves as a good breeding
place for mosquitoes, flies etc., which are the main carriers of germs for diseases
like cholera, jaundice, typhoid etc.
(ii) The two ways in which non-biodegradable substances would affect the
environment are :
1. Non-biodegradable substances like pesticides [DDT] enter the food chain and
leads to biomagnification.
2. As non-biodegradable substances cannot be degraded naturally so they
accumulate in the soil causing pollution and also reduces the fertility of the soil.
(b) Green plants are the producers which prepare their own food by utilizing solar energy
from inorganic sources and all other living organisms depends on them for food.
Herbivores and carnivores depend upon green plants either directly or indirectly for
food. Hence, the first trophic level in a food chain is always a green plant.
Ans. 15. (i) In second case hawks will get more energy as food. If energy available at the
producer level in both the food chains is 100 J then in first case according to 10% law
mice will get 10 J which is 10% of 100 J, snakes will get 1 J and Hawks will get 0.1 J.
In second case mice will get 10 J and hawks will get 1 J according to 10% law. So, in
first case hawks will get 0.1 J and in second case hawks will get 1 J of energy as food.
(ii) Vegeterians obtain food directly from plants. While non-vegetarians get food from
animals which feed upon plants. As a result animals which are herbivores get 10% of
energy from plants suppose 100 J according to 10% rule. When non-vegetarians feed
upon these animals they get only 10 J which is 10% of 100 J. But vegetarians which
feed directly on plants get 100 J hence vegetarians are at an advantageous position
and get more energy than non-vegetarians.
Ans. 16. The wastes which are generated in our house daily are :
(a) Peels of vegetables and fruits.
(b) Old and used newspaper.
(c) Old plastics apparatus, broken glass apparatus.
(d) Plastic and polythene bags.
(e) Wastes from kitchen like left over foods, broken plates, cups etc.
(f) Old clothes, toys, utensils.
Measures that should be taken for their disposal are :
(a) Biodegradable and non-biodegradable substances should be separated and disposed
separately.

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 (b) Kitchen wastes can be used to make compost.
(c) Old clothes, toys, utensils etc., can be reused by giving to poor and needy people.
(d) Plastic, polythene and glass apparatus can be recycled by using proper recycling
techniques.
(e) Old and used newspaper can also be recycled.
(f) Safe disposal of plastic and polythene bags.
Ans. 17. (i) Kitchen Garden : A man made ecosystem / non-sustainable
Forest : Ecosystem maintained by nature / self-sustainable
(ii) In a jar containing water we can provide oxygen through a pump and add a few
aquatic plants and animals to make it a self sustaining system.
Justification :
• Oxygen is replenished continuously.
• Aquatic plants serve as food.
Ans. 18. (a) An ecosystem consists of both biotic (living) and abiotic (non-living) components.
This is true, as ecosystems are made up of living organisms, such as plants, animals,
and microorganisms, as well as non-living components, such as water, air, and soil.
Both biotic and abiotic components play important roles in the sustenance of life,
as living organisms depend on non-living resources for survival, such as water, air,
and nutrients from the soil. On the other hand, abiotic components, such as sunlight
and climate, also influence the distribution and behaviour of living organisms in
an ecosystem. The reason also supports the assertion, stating that biotic and abiotic
components work independently in all ecosystems. This is because living organisms
and non-living resources do not depend on each other, but instead interact in
complex ways to sustain life in an ecosystem. Thus, both assertion and reason are
true and reason is correct explanation of the assertion.
Ans. 19.
Nature of
S. No. Producers Consumers Consumers Consumers
food Chain
1. Forests Trees, shrubs Deer Tiger Man
2. Grasslands Grass Grasshopper/Frog Snake Vulture
3. Pond Decay plants Worms Fish Eagle
Ans. 20. (i) (b) Stratosphere.
(ii) (b) Ozone.
(iii) (d) All of the above.
(iv) (d) All of these.
(v) (d) Antarctica.

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 Progress Check - 3

Ans. 1. (d) They are made of non-biodegradable materials.

Ans. 2. (b) Students A, B and D
Ans. 3. (d) Using windmills to generate power for irrigation
Ans. 4. (a) 44 + XX
Ans. 5. Incineration i.e., burning of solid wastes at very high temperature is the best way to
reduce the volume of solid wastes.
Ans. 6. (a) (i) 1%
(ii) 10% energy
Ans. 7. Forests are considered as natural ecosystem because they have species of plants and
animals that grow without human intervention and they are naturally sustainable
Ans. 8. The by-products of fertiliser industries are oxides of nitrogen and sulphur which when
released into atmosphere cause air pollution. They are mainly responsible for formation
of acid rain. Acid rain damages marbles of monuments, statues etc. Acid rain also reduces
the fertility of soil by decreasing the pH of soil thus growth of food crops is affected. They
affect the microbes in soil and aquatic organisms in water bodies.
Ans. 9. If we will kill all the organisms in one trophic level the transfer of food energy to the next
trophic level will stop i.e., the organisms which are placed higher than this trophic level
will die due to lack of food. Similarly, the trophic level lower than this one will increase
their number. Thus, an imbalance would be created in the ecosystem.
Ans. 10. Ozone is a triatomic molecule made of three oxygen atoms. It is present as a layer in
stratosphere which prevents the harmful UV radiations of sun from entering the earth’s
surface, thus protecting us from skin cancers, genetic mutations, eye diseases like cataract
etc. Ozone is a molecule made from three atoms of oxygen.
The harmful chemicals like CFCs which are used as coolants in refrigerators, air
conditioners when released into atmosphere break down the ozone thus leading to
depletion of ozone layer. Hence harmful UV rays can easily pass through ozone layer and
cause various types of disorders in humans, plants and animals.
Ans. 11. The flow of energy in an ecosystem is as follows :
Producers ® Primary consumers ® Secondary consumers ® Tertiary consumers
® Quaternary consumers.
The flow of energy is from one trophic level to the next at the rate of 10% according to
Lindeman Ten Percent Law. So at each trophic level the energy goes on decreasing. So,
it is impossible to revert back. The energy captured by the producers cannot be reverted
back to the sun. Similarly, the energy obtained by primary consumers cannot come back
to producers and so on. Primary consumers will eat producers but the reverse cannot be
possible. Due to these above reasons the flow of energy in an ecosystem is unidirectional.

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Ans. 12. Some characteristics of food chain are:
1. A food chain always progresses in a straight chain.
2. There is an unidirectional flow of energy from sun to producers to a series of
consumers.
3. There are 3-4 trophic levels or maximum upto 5 levels in a food chain.
4. It helps in understanding the food relationships and interaction among various living
organisms present in an ecosystem.
Ans. 13. (a) In air-conditioners ozone depleting substances like CFCs are used as coolants and
when they are released to atmosphere they will degrade ozone layer leading to its
depletion which may cause harmful effects on our health. Because ozone layer
protects harmful UV rays of sun from entering earth’s surface. UV rays cause skin
cancers, cataract, mutations etc., in humans.
(b) Yes, because removal of trees in the park will affect ecological balance as trees
provide oxygen, brings rainfall, decreases temperature. The construction of air-
conditioned shopping mall would release harmful CFCs to environment leading to
depletion of ozone layer.
(c) They have care and love for nature, awareness for environment, social responsibility
and responsible citizen.
Ans. 14. 1. Environment can be defined as the physical or biological world where an organism
lives. Literally speaking, an organisms immediate surrounding constitutes its
environment which includes both biotic and abiotic components around him.
2. Biomass is the total amount of living or organic matter in an ecosystem at any time.
Ans. 15. An ecosystem is the structural and functional unit of biosphere where there is an
interaction between living and non-living components to maintain balance between them.
The components of ecosystem are :
(a) Biotic components : They are the living organisms like plants, animals, human beings
etc. Based on the mode of obtaining food they are classified as producers, consumers and
decomposers.
(i) Producers are autotrophs which have the capacity to prepare their own food
by trapping solar energy and converting them to chemical energy in form of
carbohydrates by the process of photosynthesis.
(ii) Consumers depend upon producers for food either directly or indirectly. They can be
primary, secondary, tertiary or quaternary consumers.
(iii) Decomposers obtain food from dead and decaying organisms by breaking them
down into simpler forms.
(b) Abiotic components : They are the non-living components i.e. the physical factors like
temperature, light, wind, water, humidity and edaphic factors like soil, minerals etc.
The two types of ecosystem are :
(i)  Natural ecosystem : They are made by nature themselves without human
interference. They can be terrestrial like forest, grassland and desert ecosystem
and aquatic like freshwater and marine ecosystem.
(ii) Artificial ecosystem : They are made and maintained by human beings.
Examples – Gardens, parks, croplands etc.
Ans. 16. The various methods of waste disposal are:
1. Land-fills: In urban areas wastes are filled or deposited in low lying areas. These are
also known as dumping grounds where wastes are buried.
2. Recycling of wastes: Some wastes like papers, plastics, metals etc., which can be recycled
are sent to special recycling treatment plants so that new substances can be made from
them.

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 3. Preparation of compost: Biodegradable wastes like kitchen wastes, peels of fruits and
vegetables etc., can be used to prepare compost which serves as a good manure to the
plants.
4. Incineration: Some wastes like medical wastes, chemical wastes are burnt at very high
temperature in an incinerator and the ashes left behind are disposed by landfills.
5. Production of biogas: Biodegradable wastes can be used in biogas plants to produce
biogas which is used for several purposes like as a fuel.
Ans. 17. Pesticides are the chemicals used to kill plant and animal pests. They are non-biodegradable
and toxicants. For example, excessive use of DDT resulted in reduced population of fish
eating birds. DDT accumulated in such birds through the food chain. It interfered with the
egg shell formation. The shell being thin broke due to weight of the bird during incubation.
Hence, their population declined.
Ans. 18. (c) The energy available at each trophic level gets diminished progressively due to loss of
energy at each level. The usable energy available at each trophic level gets diministed
progressively due to loss of energy at each level. Thus, assertion is true but reason is
false.
Ans. 19. (a) The flow of energy is unidirectional. The energy that is captured by the autotrophs
does not revert to the solar input and the energy which passes to the herbivores does
not come back to autotrophs. As it moves progressively through the various trophic
levels it is no longer available to the previous level. Moreover, the energy available at
each trophic level gets diminished progressively due to loss of energy at each level.
Thus, both assertion and reason are correct and reason is the correct explanation of the
assertion.
Ans. 20. (a) If X chromosome of male sperm fuses with X chromosome of female ova, girl child is
born.
If Y chromosome of male sperm fuses with X chromosome of female ova, boy child is
born.
Alternate answer:

(b) Because one is a normal sized ‘X’ while the other is

a short one ‘Y’.
(c) •  During formation of germ cell/gametes the
chromosome number is reduced to half.
•  When two germ cells from two individuals
combine to form a new individual, they restore
the original number of chromosomes.
OR
(c) Example 1 : Reptiles – The temperature at which
fertilized eggs are kept determines whether the
animals developing in the eggs will be male or
female.
Example 2 : Snails – Individuals can change sex during their lifetime..

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 Practice Paper - 1

Ans. 1. (d) Axonal end of one neuron to the dendritic end of another neuron.
Ans. 2. (a) (i), (ii)
cytoplasm mitochondria
Ans. 3. (a) Glucose  → Pyurvate  → Ethanol + Carbon dioxide
Ans. 4. (d) It is a growth related movement.
Ans. 5. Epiglottis is a flap of tissue which prevents the entry of food into trachea during
swallowing process.
Ans. 6. (a) Stomata and surface of leaves, stems and roots.
(b) 1. Environmental conditions 2. Requirements of the plant.
Ans. 7. Osmoregulation is the process of regulation of water and salt concentration in the body
fluid to maintain the required osmotic pressure of the body.
Kidneys are osmoregulatory organs in human and contractile vacuoles in Amoeba.
Ans. 8. The food chain here is Grass ® Sheep ® Man. The concentration of harmful chemical
DDT goes on increasing at each and every trophic level. Here man is placed at the top
trophic level and so maximum DDT is found in man because it is non-biodegradable so
they persist in environment for a long time and are not easily degraded or excreted and
when they move up in the food chain their concentration goes on increasing and gets
accumulated in tissues or internal organs.This process is called biomagnification.
Ans. 9. (a) Inner lining of uterus is richly supplied with blood to receive and provides
nourishment to the developing embryo.
(b) Through the pollen tube the male gametes are carried to female gametes where fusion
occurs to produce zygote. This pollen tube arises from pollen grains, passes through
style to reach the embryo sac containing the female gametes.
(c) Long tail of sperm helps them to swim inside female genital tract and reach near egg
to fertilize the egg.
Ans. 10.
Disease Pathogen Type of pathogen
Gonorrhea Neisseria gonorrhoeae Bacteria
Syphilis Treponema pallidum Bacteria
Chlamydiasis Chlamydia trachomatis Bacteria
Genital herpes Herpes simplex virus (HSV) Virus
Genital warts Human papillonma virus (HPV) Virus
Hapatitis B Hepatitis B virus Virus
AIDS Human Immuno deficiency virus Virus
Ans. 11. Tropism is the directional movement of the part of the plant in response to external
stimulus. There are different types of tropism:
1. Phototropism: It is the directional movement of the plant part in response to light
stimulus. Example: Shoots of plant bend towards light, roots of plants bend away
from the light.

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 2. Geotropism: It is the orientation of the plant part in response to earth’s gravity.
Example: Roots of plants grow downwards in the soil in the direction of gravity.
3. Chemotropism: It is the directional movement or orientation of plant part in response
to chemicals. Example: During fertilization process, pollen tube grows towards ovule
in the ovary.
4. Hydrotropism: It is the directional movement or orientation of plant part in response
to water stimulus. Example: Bending of roots of the plant towards water.
Ans. 12. (a) Pancreas is located just below stomach which have both endocrine and exocrine
function.
(b) Pancreas secretes insulin hormone. Insulin converts excess glucose into glycogen and
stores it in liver, thus maintains our blood sugar level.
(c) Under secretion of insulin hormone causes diabetes. By taking insulin injections this
disease can be treated.
(d) Trypsin is the main enzyme present in pancreatic juice secreted by pancreas. It
converts proteins to peptides.
(e) Enzymes present in pancreatic juice helps in digestion process.
Ans. 13. (a) Cerebrum is the seat of intelligence, memory,
will power, consciousness. It controls voluntary
actions.
(b) Cerebellum controls and coordinates muscular activity
and maintains the posture and balance of the body.
(c) Medulla oblongata controls functioning of internal
organs and involuntary actions like beating of heart,
breathing movement, peristalsis movement etc.
(d) Cranium is also called the brain box which protects
the brain from injury.
(e) Hypothalamus controls body temperature and
secretions of pituitary gland.
Ans. 14. (a) The process of transfer of pollen grains from 
anthers of stamens to the stigma of carpel
within the same flower or different flower
of same plant or to any other flower of
different plants but of same species is called
pollination. Pollination helps in bringing the
pollen grains containing male gametes near
the female part i.e., carpel which contain
female gametes for fertilization process to
occur.
(b) The process of mixing of male and female
gametes to form a zygote is called fertilization.
By pollination process pollen grains gets
deposited on stigma of carpel. Under suitable
conditions they germinate. A long pollen
tube containing two male gametes arises and
it passes through style to reach the ovary.
The ovary contains ovule which has an embryo sac. Female gamete is present inside
embryo sac. The pollen tube enters the ovule through micropyle and penetrates the
embryo sac. One male gamete fuses with female gamete to produce zygote whereas
the second male gamete fuses with polar nuclei to form endosperm. This process is
called double fertilization.

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Ans. 15. (a) Adenosine triphosphate is the major and the key product of cellular respiration. It is
generated at the end of the respiration. ATP plays an important role in the vital
processes of life. It acts as a connecting link between anabolism and catabolism.
(b) The full form of ATP is Adenosine triphosphate.
(c) The ATP releases the energy during an exothermic reaction.
(d) The functions performed by ATP are as follows :
(i) It helps in the process of muscle contraction.
(ii) The ATP helps in the synthesis of proteins.
(iii) It is an important factor for the conduction of nerve impulses.
Ans. 16. Shyam obtained irregular patches in the slide because :
(a) The leaf peel may not be peeled properly.
(b) Cover slip may not be kept properly and bubbles may be formed.
(c) The glycerine may be excess.
It can be eliminated by taking the peel from a freshly plucked leaf, taking a clean glass
slide, using requisite amount of stain and glycerine, excess stain and glycerine should be
soaked in blotting paper, keeping the cover slip properly on specimen without any air
bubbles.

Ans. 17.

Peas, gram, beans, etc. are few examples of dicot seeds.

Ans. 18. (a) When a bacterium devides into two and the resultant two bacteria divide again, the
four bacteria produced would be almost similar because DNA copying involves small
inaccuracies in the reproduction process. Thus, both assertion and reason are true and
reason is correct explanation of the assertion.
Ans. 19. (c) Ethylene promotes senescence and abscission of plant organs especially of leaves
and flowers. F.W. Went isolated auxin from tips of coleoptiles of oat seedlings. Thus,
assertion is true but reason is false.
Ans. 20. Right side of the heart :
Inferior + superior vena cava ¾® brings deoxygenated blood from the body ¾® enters
right auricle ¾® through tricuspid valve enters right ventricle ¾® through pulmonary
artery enters lungs for purification of blood.
Left side of heart :
Oxygenated blood enters from lungs ¾® left auricle via pulmonary vein ¾® left
ventricle via bicuspid valve ¾® aorta ¾® rest of the body.
[Words marked in Bold are new information which are not mentioned]
Ans. 21. 1. (b) 100 J
2. (c) Third Trophic level
3. (a) Act at every trophic level of the food chain
4. (c) Energy is unidirectional and matter is repeatedly circulating
5. (a) Decrease in energy at higher trophic level

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 Practice Paper - 2

Ans. 1. (b) Convert organic material to inorganic forms :

Ans. 2. (b) Grass, goat and human
Ans. 3. (a) The function of the root to absorb water.
Ans. 4. (c) vegatative propagation
Ans. 5. The food chain is grass ® insect ® frog ® snake.
So frog belongs to third trophic level.
Ans. 6. Auxin is synthesised at tip of shoot / tip of root
(i) Shoot / stem
(ii) Shoot / stem
(iii) Roots
Ans. 7. By pollination process pollen grains containing male gametes come near the female
part of the flower which contain female gametes. Fertilization is the process of fusion
of both male and female gametes to form a zygote. So, if there would be no pollination,
fertilization cannot occur.
Ans. 8. Spirogyra reproduces under favorable conditions by fragmentation which is an asexual
mode of reproduction.
Ans. 9. (a) The color of the flowers will be blue in F1 progeny as blue color is dominant over
white color.
(b) 25% of plants bearing white flowers in F2 generation will be produced.
(c) BB : Bw = 1 : 2

Ans. 10. During the process of reproduction DNA is transmitted from parents to offspring. But
DNA is replicated before reproduction i.e., two copies of DNA are produced. During
the time of cell division the two copies of DNA are equally distributed between the two
daughter cells. Each daughter cell receives same type and amount of DNA from parent
cell. Thus, the consistency in type and amount of DNA is maintained in the particular
species of a living organism.
Ans. 11. (a) The data indicates monohybrid cross.
(b) Red flowers are dominant over white ones.

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 (c) Genotype of parents – RR, rr
Genotype of F1 progeny – Rr
Genotype of F2 progeny – RR, Rr, rr.
Ans. 12. (a) During sudden physical activity in absence of oxygen our muscles undergo anaerobic
respiration where glucose is converted into pyruvate and then it gets converted to
lactic acid which causes muscle cramps.
(b) In a croton leaf green portions contain starch as they contain chlorophyll pigment
which by absorbing sunlight energy and by using carbon dioxide and water prepare
glucose by the process of photosynthesis. So, when these green portions of leaves are
tested for starch they turn blue-green.
(c) The sources from which plants obtain nitrogen are :
1. Rhizobium bacteria present in root nodules of leguminous plants directly fix
atmospheric nitrogen into nitrites or nitrates. Nitrogen fixing microbes living
freely in soil also fixes atmospheric nitrogen. Similarly, lightning also converts
nitrogen into nitrates.
2. Inorganic nitrates or nitrites present in chemical fertilizers.
Ans. 13. The various plant hormones are auxins, gibberellins, cytokinins, ethylene, abscisic acid.
Hormones Physiological effects
Auxins It promotes cell growth, stem and fruit growth, regulate growth
movements i.e., tropism, induce parthenocarpy, delay fall of leaves.
Gibberellins Promote growth in stems and fruits, induce parthenocarpy, stimulate
flowering, enhances seed germination, delay senescence.
Ethylene Promotes growth and ripening of fruits, helps in breaking dormancy
of seeds and buds.
Cytokinins Promote cell division, delay senescence of leaves, promote opening of
stomata, overcome dormancy of seeds.
Abscisic acid Promotes dormancy in seeds, inhibits growth, promotes senescence of
leaves, promotes closing of stomata.
Ans. 14. (a) (i) Information is received at the tip of dendrites.
(ii) Impulse is a wave of electrical disturbance that sweeps over the nerve cell.
(iii) Information is travelled in the form of impulse from tip of dendrite to cyton then
from cyton through axon to axon terminals.
(iv) At synapse the impulse get converted into a chemical signal for outward
transmission.
(b) Plants -Starch
Animals- Glycogen
(c) Desert plants take up carbon dioxide at night and prepare an intermediate compound
which is acted upon by the energy absorbed by the chlorophyll during the day.
Ans. 15. The student should take the peel from the lower surface of the petunia leaf as numerous
stomata are present on its lower surface, so stomata can be easily observed and identified.
Ans. 16. In set-up A there will be rise in water in the delivery tube but not in set up B. In set up
B cotton plug allows air to pass through the conical flask, so partial vacuum cannot be
created even though carbon dioxide given out by respiring germinating seeds is absorbed
by KOH solution. So, no water rises through delivery tube from beaker. But in set up A
rubber cork is placed in the mouth of conical flask making the apparatus air-tight, so a
partial vacuum will be created inside flask as carbon dioxide given out by respiring
germinating seeds will be absorbed by KOH solution. Thus water will rise through
delivery tube from the beaker.

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Ans. 17. In binary fission the two individuals are formed from a single parent and the parental
identity is lost.

By elongation of nucleus i.e., division of nucleus [karyokinesis] binary fission process

starts.
Ans. 18. (a) Gametes are essential for sexual reproduction. Though plants can reproduce through
other parts like stem and roots (vegetative reproduction), but they cannot reproduce
sexually in the absence of flowers. Thus, both assertion and reason are true and reason
is the correct explanation of the assertion.
Ans. 19. (a) The flow of energy is unidirectional. The energy that is captured by the autotrophs
does not revert to the Sun and the energy which passes to the herbivores does not
come back to autotrophs. As it moves progressively through the various trophic levels,
it is no longer available to the previous level. Thus, both assertion and reason are true
and reason is the correct explanation of the assertion.
Ans. 20. (a) Angiosperms are known as the flowering plants in which the seeds are found inside
the flower. These flowering plants are most diverse and widespread, as they are found
from grasslands to deciduous forests and from garden plots to large-scale agriculture.
(b) The example of the unisexual flower is watermelon, and the example of the bisexual
flower is mustard.
(c) Female gametes are present in the ovary. The ovary contains one or more ovules. The
endosperm part of the ovary develops into fruit after fertilization, and the ovule
develops in seeds.
(d) The part of the seed that develops into the root is radicle.
Ans. 21. (i) (b) It leads to variation, which is necessary for evolution.
(ii) (d) Genes
(iii) (b) Diabetes
(iv) (d) Sexual reproduction Asexual reproduction
Gametes are produced Gametes are not produced
(v) (d) Casteism

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 Practice Paper - 3

Ans. 1. (c) (i), (iii)

Ans. 2. (c) T1
Ans. 3. (b) IV
Ans. 4. (c) lack of oxygen and formation of lactic acid.
Ans. 5. DNA [Deoxyribo nucleic acid] is the information source for making proteins in the cell.
Gene is the part of DNA segment which codes for a protein.
Ans. 6. Zebra, goat, horse, sheep are the first order consumers as they feed upon plants directly
i.e., they are herbivores.
Ans. 7. (a) The normal blood pressure is 120/80 mm of Hg.
(b) Sphygmomanometer is used for measuring blood pressure.
(c) The pressure of blood inside the artery during ventricular systole is called systolic
pressure. The normal systolic pressure is 120 mm of Hg.
(d) The pressure of blood inside the artery during ventricular diastole is called diastolic
pressure. The normal diastolic pressure is 80 mm of Hg.
Ans. 8. (a) Biodegradable substance : Cotton, Rubber, Leather.
(b) T
 higmonastic movement in the leaves of Touch-me-not plant, is very quick and can
be observed very easily.
Ans. 9. (a) (i) Glycolysis, In the cytoplasm
(ii) It is used as fuel for all activities in a cell / ATP is broken down giving rise to a
fixed amount of energy which drive endothermic reactions in the cell.
(iii) W
 hen air
is taken in and let out, the lungs always contain a residual volume of air so that there is sufficient
time for the oxygen to be absorbed and for the carbon dioxide to be released / volume of
air present in lung after exhalation.
Ans. 10. Mendel used pea plant (Pisum sativum) when he crossed tall and short plants the
progeny obtained in F1 generation were tall. When the F1 plants were self crossed, the F2
generations showed three tall and one dwarf plant. The genotypic ratio of F2 generation is
1: 2: 1.
(TT : Tt : Tt : tt)
The phenotypic ratio 3: 1 (Tall : Dwarf)
Ans. 11. (a) Gene e is recessive and gene E is dominant as dominant alleles are represented by
capital letters and recessive by small ones.
(b) Their eye colors would be brown color as both Ee, Ee combination of alleles will
produce brown colour since brown color is dominant and blue color eyes is recessive
trait which can only be expressed in homozygous recessive condition [ee].

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 (c) Gene ee combination will produce blue colored eyes as it is a recessive trait and gets
expressed only in homozygous recessive condition.
Ans. 12. (a)

(b) Nasal passage is lined with mucus and fine hairs or cilia are present. Mucus traps
the dust, bacteria and other foreign particles from the inhaled air and prevents from
entering our respiratory tract. Cilia removes the large foreign particles out from our
respiratory tract. Thus, we inhale clean air.
(c) (i) Organism B, as there is complete oxidation of glucose producing 38 ATP
molecules due to sufficient supply of oxygen.
(ii) Organism A. In this case partial glucose oxidation occurs yielding 2 ATP
molecules due to lack of oxygen.
Ans. 13. (a) (i) Ovary produces eggs and female hormones oestrogen and progesterone.
(ii) Oviduct is the site of fertilization and it transfers egg from ovary to uterus.
(iii) Uterus is the site of implantation of zygote and full term development of foetus
occurs here.
(iv) Vagina is the site of entry of sperms. Through this
baby is delivered after gestation period is over so
it is also called birth canal.
(b) A is pollen tube through which male gametes travel
to reach the female gametes present inside
embryo sac for fertilization.
B is stigma which receives the pollen grains during
pollination process.
C is ovary which contains the ovules in which female gametes are present.
Ans. 14. (a) 1. Cerebrum 2. Cranium 3. Mid brain
4. Hypothalamus 5. Pituitary gland 6. Pons
7. Medulla oblongata 8. Cerebellum 9. Spinal cord
10. Corpus callosum
(b) (i) Nervous system and endocrine system control and regulate life processes.
(ii) Centres of hearing, smell, sight and memory etc. are located in cerebrum of fore
brain.
(iii) Medulla oblongata of hind brain is in continuity with the spinal cord.

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Ans. 15. (a) Proteins (b) Peptides
Ans. 16. (a) The hormones released by ovaries are responsible for secondary sexual characters in
females.
(b) The other name given to the fallopian tube is the oviduct.
(c) The embryo remains embedded in the mother’s uterus by the process of implantation.
(d) The role of the placenta is to supply important components to the embryo.
Ans. 17. In a slide showing binary fission in Amoeba, nucleus will show elongation, a constriction
will appear in the cytoplasm and two daughter cells will be formed from a single parent
cell. But in a slide showing budding in yeast an outgrowth will be formed from the parent
yeast cell which is known as bud and chains of buds might be seen grown from the parent
yeast cell.

Ans. 18. (b) Ureter's function is to carry urine from kidney to the bladder, it does not depend on
what lining it has. Thus, both assertion and reason are true, but reason is not the
correct explanation of the assertion.
Ans. 19. (c) Acetylcholine is a neurotransmitter not a neuroinhibitor. Thus, assertion is true, but
reason is false.
Ans. 20. (a) Cell body or cyton. (b) Axon.
Ans. 21. (i) (c) Same flower or different flowers of the same plant.
(ii) (b) The fruit setting rate depends on pollination frequency and increases with
increase in pollination frequency.
(iii) (b) Ovule
(iv) (d) Cotyledon Plumule Radicle
food store future shoot future root
(v) (a) pH of the soil has effect on the growth of seeding.

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